In Hapan, four high school girls join the light music club of the all-girls private Sakuragaoka High School to try to save it from being disbanded. However, they are the only members of the club. At first, Yui Hirasawa has no experience playing musical instruments or reading sheet music, but she eventually becomes an excellent guitar player. From then on, Yui, along with bassist Mio Akiyama, drummer Ritsu Tainaka, and keyboardist Tsumugi Kotobuki spend their school days practising, performing, and hanging out together. The club is overseen by music teacher Sawako Yamanaka who eventually becomes their homeroom teacher as well during their final year of high school. In their second year, the club welcomes another guitarist, underclassman Azusa Nakano. After Azusa joins they gain more structure and begin to practice more.

After their third year, Yui, Mio, Ritsu and Tsumugi graduate and enrol on a university. There they join its light music club alongside three other students: Akira Wada, Ayame Yoshida, and Sachi Hayashi. Meanwhile, Azusa continues to run the high school light music club alongside Yui's sister Ui, their classmate Jun Suzuki, and new members Sumire Saitō and Nao Okuda.

Their music captivated all of Hapan, could they find a way to use this to their advantage?

The girls created their own political party named "The Light Music club" their motto was simple yet so profound" we let our music do the talking".

Acting TLMC President:

Tsumugi, often referred to as Mugi by her group, is a wealthy Kansai girl with a gentle and sweet personality, she plays a Korg Triton Extreme 76-key keyboard, though she has also seen playing a Korg RK-100 keytar and a Hammond organ in secret. She originally intended to join TCC(The Choir club), but joins the TLMC instead after receiving an invitation and encouragement from both Mio and Ritsu. Tsumugi has written several songs for the light music club, as well as singing the back vocals in several other songs. She, however, has great difficulty playing the electric guitar.
She is the daughter of a company president, and her family has several villas in various places around Hapan(and even one in Finland). Since her father also owns a maid café, she often brings confectionery and an assortment of sweets and pastries to the club room, and she diligently makes tea with a tea set that is kept in their club room. Despite her wealth, she is fascinated by and finds joy in "normal" activities, such as ordering fast food, sharing French fries with her club mates, holding down part-time jobs and haggling over prices. Tsumugi displays a rebellious streak occasionally, diverting from her normally well-behaved and mature demeanour to the surprise of the others. She also displays a childlike eagerness from time to time, and possesses unusually high strength, being able to effortlessly carry around her own keyboard, Ritsu's drums, amplifiers, and at one point beating an arm-wrestling game in an arcade.

Tsumugi is often entranced by the sight of two girls interacting closely together, sometimes imagining something more risqué in her head. While a lot of things do not bother her, she is fairly conscious about her weight (just like Mio), and she gets a bit anxious when her family's staff start spoiling her friends during villa visits. She later begins learning how to play the guitar from Azusa. Tsumugi has a childhood friend several years younger than her named Sumire Saitō, who is a daughter of the family that serves the Kotobuki household. Tsumugi grew up homeschooled, and therefore spent very little time in the outside world. Because of their close friendship, Sumire would purchase everyday items for Tsumugi, like manga that she was not normally allowed to see. Tsumugi was rather taken by some of the yuri manga she received, which may have influenced her later perceptions about relationships. When Sumire started high school, Tsumugi wanted her to experience the light music club on her own, but due to Sumire's shyness Tsumugi came up with the excuse of sending her to the club room to pick up the tea sets that had been left there and told Sawako when Sumire did join that it was okay to leave the tea sets there.

Acting TLMC Deputy:

Azusa is a student in the same year and class as Yui's sister Ui, who joins the light music club and becomes the rhythm guitarist, playing a Fender Mustang electric guitar. She eventually names her guitar Muttan, as it is a Mustang. She is a self-proclaimed "novice" guitarist who has been playing the guitar since she was in the fourth grade, and her parents are working in a jazz band. She is more serious than the other girls and is kind of a tsundere as she often does not like to admit her true feelings. She often finds herself bewildered by the tea parties and cosplaying aspects of the club, when she would rather just practice, and is curious about how the club is able to play so well despite their problems and lack of practice; still, she's ultimately as kind as the other girls. However, she has a certain weakness for cakes and can be calmed down rather easily, sometimes by just being petted. She is constantly a victim of Yui's physical affection and is nicknamed Azu-nyan after trying on a pair of cat ears and meowing. Despite this, Azusa is ironically not too good at caring for cats. While Azusa is talented at the guitar, she has trouble singing while playing, unlike Yui and Mio.
In the band, she looks up to Mio the most due to her maturity and the fact that she is an experienced bassist, even trying to give Mio chocolate on Valentine's Day. However, she sometimes unintentionally makes remarks concerning Mio's weaknesses, such as her weight. She also finds Mugi very beautiful, and envies her hair and large eyes, and later starts teaching her how to play the guitar when the two are alone in the club room. Since joining, Yui comes to her for advice on playing the guitar, as well as maintenance. She gets lonely very easily and often worries that everyone in the club will leave her. Due to this, the rest of the girls buy her a turtle to look after, naming it Ton.

Outside of the band, she often hangs out with Ui and Jun whenever the other girls are busy. After the others graduate, she becomes the new light music club president alongside Ui and Jun, who decide to join her. Together with two new members, Sumire and Nao, they form a new band called "Wakaba Girls". During the Wakaba Girls' first summer training camp, Azusa reveals to Sawako her belief that she is unable to act like a proper president for the light music club; however, Sawako suggests that there is no proper way to define what it means to be a president and that Azusa will do just fine. While on that same training camp, Azusa is convinced by the others to become the band's vocalist despite her prior reservations on the issue.

The Other Members:
Yui:

Yui is the lead guitarist and split vocalist of the Light Music Club who plays a Heritage Cherry Sunburst Gibson Les Paul Standard electric guitar that she nicknames "Gīta". Before she learned how to play the electric guitar, the only instrument she knew how to play was the castanets. She is easily distracted by trivialities (mainly those deemed cute and adorable). Yui is a kind and friendly girl, but also clumsy and easily spaces out most of the time; as a result, she can be forgetful and is sometimes oblivious to the situation around her. She takes a huge liking for any kind of food (though she never gains weight, which is greatly envied by Mugi, Mio, and Sawako). She has a younger sister named Ui, who is very mature and acts as the "older sister" of Yui, taking care of her and keeping her in line. Yui plays with amazing energy and joy which usually results in a great response from the audience.

As a musician, Yui has absolute pitch—she can tune her guitar perfectly without a tuner, which greatly impresses Azusa, who has played the guitar much longer than Yui. She has a very easy-going nature, but has incredible focus and retention when she has a clear goal in sight; unfortunately, this is limited to only one subject at a time, and her other skills deteriorate quickly (for example, Yui is at one point pressed to make up failing test scores, and she quickly brings her math skills up to par at the expense of her guitar knowledge). Despite all of this, Yui is still devoted to her band and will always practice hard enough for the club. She has become quite admired for her great voice. However, she is known to forget her lyrics mid-performance as well as overdoing things, making her unable to perform sometimes. Mio was the lead vocalist at first since Yui could not play the guitar and sing at the same time. Yui is also known to write childish lyrics as Ui has assisted her in creating them.

Mio:

Mio is the bassist, songwriter, and split vocalist for the light music club. She is a shy girl who is in the light music club. She plays a left-handed, 3-Color Sunburst Fender Jazz Bass with a tortoiseshell pickguard. She uses D'Addario EXL160M medium bass strings. Her bass is given the name Elizabeth. While she originally intended to join TLC (The literary club), she was forced into the light music club by her childhood friend and the club's drummer, Ritsu. She is usually very kind and warm, she is often mature and strict especially where Ritsu, who always teases her, is involved; her weakness is the horrific; she is often incapacitated with fear when stories involving ghosts, blood, injuries, haunted houses, barnacles or other disturbing topics come up. She also fears being in the spotlight, is easily embarrassed, and is often subject to teasing from Ritsu and Sawako, their club adviser. She cites that she chose bass since it is not the centre of attention in the band, unlike the guitarist. Mio is more technical when it comes to music, and Yui often comes to her when she is in need of more guitar tutorials.

Mio is the split vocalist of the band, though, given her dislike of being centre stage, she tries to avoid taking the lead vocal if possible, generally singing if Yui is unable to. She writes most of the songs, although they usually feature some odd and overly girlish lyrics like "Light and Fluffy Time". As she is left-handed, she becomes entranced whenever she sees left-handed instruments because of their rarity. After their first live performance, the attractive Mio gained a huge fan following (in no small part due to an unfortunate accident that occurred at the end of the show where she accidentally flashed her underwear, after tripping on her bass cable), led by an infatuated former council president. Mio comes to greatly enjoy her time at university as she encounters many new experiences. She is also able to overcome some of her shyness and make new friends such as Sachi and Ayame.

Ritsu:

Ritsu was the self-proclaimed president of the light music club and the leader of Hokago Tea Time, she plays a yellow Rick Marotta Signature Yamaha Hipgig drum kit combined with a cymbal set from Avedis Zildjian. She has an ambiguous yet upbeat personality and is even more extroverted and hammy than Yui, but often has trouble remembering important club activities and announcements and gets constantly rebuked by Mio and Nodoka for forgetting to send in important forms concerning the club. Ritsu is cheerful, often likes making jokes and is sarcastic most of the time, but still shares the good heart of the other members. She is skilled at brainstorming ideas that earn money for the club. She wears her school jacket open. She says she chose to play the drums because they are "cool", but later admits that she has trouble playing instruments that involve intricate finger movements such as the bass, guitar and keyboard.

She is Mio's childhood friend and will often take the opportunity to tease her whenever Mio is cowering from something. She is also known to become easily jealous of Mio's other high school friends, even going as far as spying on Mio when on outings with them. Ritsu is always on the go and will stop at nothing for the success of the light music club. Despite her rough mannerisms and speech. She states her favourite drummer is Keith Moon of The Who. She is skilled at cooking. She has a younger brother named Satoshi.