Bunkiten summary:

Shion has an idol childhood friend and a step sister from his dad’s 2nd marriageFor some reason, he lost his memories because he fell from the stairs, so the last thing he remembered was the night of june 6 when he was supposed to buy some crepe.After getting out of the hospital, his childhood friend suddenly told him they are dating and that it’s a secret from his sister.But, it turns out he’s also dating his sister!