The 'unintentional' aspect makes it special. In many love stories, the characters actively pursue love, but here it might be more of a gradual discovery of feelings that they didn't initially expect. This gives a more natural and unexpected feel to the relationship development.
It's hard to say when the Barnes and Noble manga sale occurs. Sometimes it's announced on their social media or in-store flyers. Keep an eye out for those!
I think 'Sasaki and Miyano' is also among the best. The story is set in a school environment. Miyano is a fudanshi (a boy who likes BL) and Sasaki is a popular boy in school. Their relationship starts from Sasaki's interest in Miyano and slowly blossoms into a deeper connection. It has a lot of cute and heart - warming moments, and the way their relationship progresses feels very genuine. It also touches on the insecurities and self - acceptance that the characters go through.
Another is 'Yuri!!! on Ice'. Although it's more sports - centered, the relationship between Yuuri and Victor is really well - developed. It shows how they support each other, grow together, and their love story unfolds in a very natural and heart - warming way. The plot also has a lot of depth with Yuuri's journey to regain his confidence in skating.