I'm looking for stories with a particular dynamic. A boy/man loves a girl/woman, but she has someone else. She still dates the hero, but it's either a sort of comfort for when she has troubles with her real boyfriend, or to give her things the main boyfriend can't/won't. For instance, one H one-shot I'd asked help finding some time ago involves a boy who had a female friend that asked to sleep with him because her boyfriend wasn't willing to go all the way yet. By the end she stopped the arrangement when her boyfriend finally consented, but the boy refused to continue the relationship because he loves her and being nothing but some guy she hangs out with sometimes hurts.

There was also something I read a long time ago, I'm pretty sure it was translated by Solaris SVU. The MC was in love with a woman, but she had a boyfriend. One day she ran to him in tears because things got bad and she ended up "breaking up" with him; they slept together, and then within days she was back together with her boyfriend. The same is implied to have continued indefinitely, with her every few weeks running to him for a comfort booty call when she fights with her boyfriend, then begging him to keep secret about it afterward when she goes back to him.

The one other thing I want is to have a story where this changes over time. At first the guy is just someone she hangs out with, seeks comfort from, maybe even sleeps with, when she's dissatisfied or fighting with her boyfriend, but eventually she starts to legitimately fall for him.