Yuma Soma:

Yuko Soma's younger brother. He has an introverted and shy personality, but he is observant and a serious student who tries to record and organize the situation even in chaotic scenes.

After the liquid accident, he turns into a black-haired girl who looks exactly like his sister and starts being called "Yu-chan" by those around him. Since his body changed while still in his male uniform, he tends to fidget, worried about his chest and hips.

He has a crush on Hinata Asakura, and when Hinata—who has become a handsome boy—approaches him, he can't hide his joy despite his confusion.

Yuko Soma:

Yuma Soma's older sister. She is cheerful and caring, having doted on Yuma for a long time. She is also Haruka Seo's girlfriend and is the bright, leader-type older sister.

After the liquid accident, she turns into a tall boy who looks exactly like her brother and is called "Yu-kun." She is bewildered by her shoulder width and deep voice but adapts quickly.

When Haruka's gaze turns toward the female Yuma, she feels as if she's being cheated on and gets jealous and confrontational.

Haruka Seo:

Yuko Soma's boyfriend and Hinata's childhood friend. A cheerful, brown-haired mood-maker. An Alchemy Club member who tends to push experiments forward on momentum; this accident is mostly his fault.

After the accident, he basically acts in his male form, but he possesses a prototype of the reaction inhibitor and checks the effects on his own body. He sometimes takes a female form from evening onwards, and he personally finds the girl life rather interesting.

Seeing Yuma in Yuko's form, he sees him as Yuko even though he knows it's Yuma.

Hinata Asakura:

A member of the Alchemy Club. Bright and friendly, she is an encourager who naturally closes the distance with anyone. She is good at making the atmosphere positive and often makes commotions bigger by siding with Haruka.

After the liquid accident, she becomes a handsome, blonde boy. She is satisfied with that appearance and tries to act like an ideal prince.

Regardless of gender, she has no sense of personal space and is a social butterfly who often makes those around her blush.

Reika Yakushiji:

The female advisor of the Alchemy Club. An adult female teacher with beautiful long hair tied in an updo, leaving an impression with her white lab coat and neat attire.

Even after the liquid accident, her outward changes are hard to notice, but a partial intersex transformation has occurred in her body.

Students ask Ms. Yakushiji to procure chemicals, show her experimental results, and come to the clubroom to hear about her beauty research. She is adored as a supportive teacher who provides a place for consultation for any worries, regardless of gender.