Shimanami Tasogare
By the mangaka who created 'Nabari no Ô'. They themself are x-gender, (is that the same as agender?), and asexual, apparently, so know first-hand both the internal struggles and the societal pressures faced by such rl people in Japan. Note: This is NOT yaoi. It does have a little shounen ai, but the focus is on the struggles of LGBT+ people, rather than their romantic/sexual relationships. It was published in a seinen magazine, hence it's not meant to be fujoshi fapping material lol. I.e. Read this for a realistic and sensitive portrayal of LGBT+ people in Japan. After this, read something by Hagio Moto, whose works inspire this mangaka.
Hollow Lovers
3.75 stars? Well I started reading this at about chapter 20 I think. I just meant to read a few pages, but ended up reading until the end! I particularly liked the way the whole coming out process was handled, and the manga's discourse on sexuality. I enjoyed the manga as a whole, even if it felt too shôjo-esque and idealised for my taste. The art was lovely. I would have liked a little more smut, but one can't expect that from a shounen ai.
Koibito No Namae