Have you seen Love Relationship? I feel like I've already recommended that to you before. Although they're more acquaintances than friends this is exactly what you're asking for.*FL is a love interest not a girlfriend
Maybe Plus Nine Boys? Idr too much cause it's been a while since I've seen the drama. ML and his friend end up liking the same girl. There's a moment where he becomes moody & jerk-ish to his friend as he tries to win over the girl.*FL is a love interest not a girlfriend
Another one with acquaintances becoming rivals to the point SML abandons friendship & acts jealous & shady is Hi! School - Love On. He doesn't steal the girl but causes a lot obstacles.*by 2/3 of the series FL & ML kinda start dating, but they aren't dating. Not an outright relationship. idr exactly tbh
Last rec that's the farthest from what you're asking is One More Happy Ending. ML & SML are both friends and end up liking the same girl. ML has a drunken marriage to FL - but it doesn't last.
Once the FL settles down & is single again,
she enters a relationship with SML.*FL is a love interest not a girlfriend
