Ikenie Touhyou(2015)

Minato lives a meek but passable high school life. This all changed when an application named "Sacrificial Ballot" appeared on her phone one night, forcing her to vote for a person from her class. Whoever "sacrificed" was said to be given "social death."

Being upset with her classmate Kana who never bothers to reply to her messages, Minato voted for her without a second thought. When the result was announced the following day, it became clear that the one vote she casted caused Kana to become the most voted person in the class. Thinking the sacrificial ballot as no more than a prank, the class quickly dismissed any uneasiness raised. Little did class 2-C know, this was simply the start of a series of disturbingly immoral events...

Chapter count includes the epilogue.