NO NTR PLSSSS PS: this is technically not "younger sister" because they are childhood friends, so it's not like "stepbro what are u doing" moment SPOILER
MC is childhood friends with FMC who has developed feelings for him. MC will fall prey to being seduced by the purple hair girl and they will fuck twice. Once at her home and once at school. FMC tries to send signals to MC but he is too dumb. The antagonist will reveal something to MC about purple hair girl and MC no longer falls prey to her seducing. MC and FMC finally express their feelings in chapter 22.
Purple hair girl keeps trying to go for MC and he refutes her later revealing that the antagonist she is sleeping with for money were friends in the past. Antagonist had committed domestic violence against the girl he was with and MC punched him and antagonist started to write bad comments about him and made his life miserable. Purple hair girl confronts antagonist and becomes victim to his comments.
MC's best friend and a girl record antagonist beating best friend up. Antagonist also tried to hurt FMC but MC beat him. Video is posted and antagonist ruined. Happy ending for MC and FMC.
