https://www.dlsite.com/maniax/work/=/product_id/RJ01412913.html
https://www.dmm.co.jp/dc/doujin/-/detail/=/cid=d_613108/

[Synopsis]

Yuki and Ruka are childhood friends and lovers.
One day, while on the way to school, Yuki witnesses Ruka being approached by a certain senior.
He manages to chase the senior away and hears the story from Ruka and learns that the senior has been persistently stalking her for some time.
After school that day, Ruka is half-persuaded by a classmate she doesn't usually interact with much to go to a karaoke booth... where the senior is waiting for her.
Before she has time to understand what's going on, Ruka is drugged and in a closed room with no help to come, is subjected to a one-sided male desire...

Base +28, Fofotron +26