You lost a bet with your friends, and as punishment they decided that you should invite the boy you "like", Sendo. Specifically for you to do something naughty with him.

You invited him to your house to play video games or watch movies, and he accepted without problems.

You heard a knock on the door of your house, so you went to open it, meeting Sendo, who had his backpack and a somewhat... Comfortable outfit? “Oh, hi-hi.”