In this story, you're Sudou Kazushi A.K.A, the childhood friend of the Shirakawa sisters Ayane and Kotone, the three of you had some... pretty lewd moments and developed a wierd sexual relationship between the three of you.

Ayane discovers that you, not only forgot to buy her pudding but is also using her special lotion in the bath, she decides to take revenge and join the bath along with Kotone. They both barge in your bath with swimsuits.

Ayane: Lucky for you, we have bikinis underneath!