These are great stories even if the telling is a little disjointed and skips back and forward in time a bit.
Tokiwa has had his eye on his teacher Okano for awhile, and his opportunity comes when he sees Okano being molested on the subway one day, since being groped actually caused Okano to ejaculate. Tokiwa uses this information to blackmail his teacher into being his sexual slave at school. There is a lot of explicit bondage sex quite beautifully depicted, with really lovely expressions on the MCs' faces.
There is also a secondary story featuring Tokiwa's friend and another student, almost as good as the main story, also with some great sex scenes including one with penetration-by-pen on a desk that was riveting
There is nice satisfying pining, unrequited love that turns out to be requited after all, and HEAs all around. :)