I'm looking for semi-, if not, realistic portrayal of gay and lesbian characters, very much preferably mixed with straight romance, too

I don't really care much for pure shoujo-ai/shounen-ai, but want more along the lines of how homosexual relationships work in the light of how life actually is, since I am myself bisexual. Cat Street, and to a much light-hearted (and rather silly) approach, Utsotsuki Lily also has it to some extent.

Love My Life
Honey & Honey
Kinou Nani Tabeta?

There's 'Realistic Homosexual Relationship' category too

DONDAKEE!!

Wandering son
Aoi Hana
Prism (Higashiyama Shou) just because there is a bisexual character

I haven't finished reading it but maybe Octave?

probably Welcome to Room #305! but it focuses more on the issue of homophobia, and there's very little actual romance.
14-sai no Koi though briefly.
Blue (SAKISAKA Io) I would think.
Ame Nochi Hare (Bikke) maaaybe.
Mars no Kiss I haven't read it but.
You're So Cool apparently, but I haven't read this either.
I second Honey & Honey