Yuuji normally returns home alone on the train after working at a convenience store, but this time it's different.
That's because the mucous life form he lives with has transformed into his colleague Takamiya and is at his workplace.
Yuuji is relieved to have finished his work without encountering Takamiya, but the slime life form happily talks to him while still transforming into Takamiya.
Because of this, he gets into trouble with the girl next to him.
She teases Yuuji and angers the slime creature, but Yuuji apologizes and calms the situation.
Yuji is calming down in the bathroom and the slime creature can't control her anger. It transforms into the girl from before to correct Yuuji's outspoken personality.
Her transformed appearance was in competitive swimsuit as she belonged to the swimming club.
Ignoring Yuuji's surprise, the slimy life form splits and transforms into Takamiya with a competitive swimsuit.
Yuuji finds it hard to suppress his sexual desire when he sees the two of them in competitive swimsuits.