Yukidoke no Koi
The teacher/student grow close but kept things professional (snow day aside), have shared interests, the student makes all advances, the teacher puts a stop to them, and only after graduation do they discuss a relationship or do anything physical. They genuinely cared for each other and I really loved their story. I especially liked that our MC came out to his best friends, who were lovely and supportive. A+ for that. His friends have their own story (and these two have a cameo!) in the manga Bokura ga Koi wo Ushinau Riyuu. I tagged both with this story's title so they're easy to find. The seventh chapter is a story of unrequited love and being someone stand-in. It's bittersweet but not hopeless. Stings, though. The second-to-last chapter is about two men who never told each other how they felt while they were at school and met twelve years later, when one is married and the other thinking about marriage. They have to hurt the people in their lives or recognize this goes no further. The final line is about a fruitless tree making fruit, so it rings hopeful. The final chapter is our MC & his sensei when the MC is away at school, on a weekend visit. :-)
Bokura ga Koi wo Ushinau Riyuu