Lesson XX

Slow building relationships shown in a sweet way. Characters questioning their sexualities while falling in love with a schoolmate. 

Slow-paced 90's slice of life anime about school life, friendship, unrequited love and romance with seaside setting. Lesson XX is BL, Umi ga Kikoeru isn't but has BL subtext as per other viewers since the pair of friends has better chemistry than the main pairing/couple. 

Lesson XX and Be-Boy tell a similar shounen-ai centred story in which two male leads go through the first awkward stages as their relationship goes from friendship to romantic. They have the same look in terms of artwork and the mood is somewhat akin, however, Lesson XX is considerably more realistic and goes in depth regarding character development while Be-Boy has a contrived plot that feels somewhat rushed.  

Shounen-ai romance with rather old fashion character designs ensures a firm kinship between these two titles. Both deal with coming to terms with same gender affection. Song is considerably darker and extremely heavy on melodrama to the point of being painful to watch, while Lesson XX is more focused on the romantic aspect; but they are both prime examples of old yaoi and probably share the same fan base. 

Fake and Lesson XX revolve around the growing romantic entanglement of two male leads. Fake has plenty of comedy and is action-packed, while Lesson XX can be described as shounen-ai, slice of life, and is spiced with romance. Both deal with the conflicts of same gender relationships and the occasionally thin line between lust and love.  

Shounen-ai in a school setting is the basic outline of both titles. Gakuen Heaven has lively artwork and develops a rather convoluted subplot along the way, while Lesson XX is rather bland in terms of artistic content and deals almost exclusively with romance. Both follow the first stages of a romantic relationship between two male characters, and lavish on dramatic moments.  

The obvious shounen-ai content is enough to warrant this recommendation. Gravitation is considerably more hyper and hilarious than the much more subdued and serious Lesson XX, but they both cover the same ground in terms of romantic overtures between two male characters.