Eh, this is a good thing for Haruto imo. He's still young and naive, with this "heartbreak", he'll realize that he can't just trust people blindly and also it will help him grow up. He's smart and talented and good looking, he will come across many better girls in his life, I think he'll turn out fine.
I don't see why some are hating on the FL, she didn't do anything wrong, from her perspective she's unaware of Haruto's feelings and chose to accept what she thinks is a genuine confession. She also shows concern for him when she learns what the other bitch has planned and tries to help him. I hope things work out well for her.
If anything though, the friend is a shitty person. Knowing that a friend who looks up to you and trusts you has feelings for a girl, and then "confessing" to her is a huge dick move, even if the intention is to "help him". And then when it backfired, he just stuck to it and was like, well, I guess we're together now. That's not what a friend does, that's what an enemy does, and I hope Haruto drops him like a bad habit.