A decent old-style BL without most old-style tropes! The main character is an ex-host going to college so he's not as young, making the college student/professor angle less iffy. Also he's not in the same dept as the professor. Reminds me of Gravitation (ironic, given the title) in that the love interest is hung up a former lover that has passed away.
This is a sequel following a third-wheel character from a previous story, but I skipped it intentionally. Wasn't interested in the plot.
Gravity Eyes