愛とか恋とか、くだらない。

He ended up in an inappropriate relationship with his childhood friend, one year his junior.

Kawai Yuuma has a childhood friend who’s a year younger than him—Kuramoto Suzuka, the sister of his best friend Kousei. To Yuuma, she’s always been like a little sister, and he thought that wouldn’t change even in high school… or so he believed.

One day, Kousei falls in love with a senior at his part-time job. “How s*upid,” mutters Suzuka, claiming she doesn’t understand romantic feelings. And Yuuma too has his own trauma when it comes to love. Yet, they’re both curious about “that kind of thing.”

“They say kissing feels good, don’t they?”

Knowing it’s wrong, they still cross that line.

The two make a promise: their inappropriate relationship will last only until they find “someone they truly love.”