I read novells The Bastard Called Brave And The Former Fiancé, I Will Crush All Of Them and The Hero Cucked Me of My Childhood Friend, so I Think I'll Steal His Fiancee.

Both novels have a common feature: the protagonist and his childhood girlfriend swore to each other in childhood to be always together, and before the main events of the novel, they are an unofficial couple. But one day an important member appears in their life, who is much higher in social status than the main character and takes the childhood friend of the main character under the pretext of helping in a certain matter.

After a while they come back and it turns out that this guy is not good (but apart from the main character nobody notices it), and the childhood friend became even worse than this guy and now despises existence of the main character.

The main character is no longer in love, dark emotions have appeared in him for the first time and he intends to take revenge on his first love and its current caretaker.

Both novels started to be translated, but after a few chapters the translation stopped and there is still no continuation, and I don't know Japanese, but I would like to know how these novels can end up.

Tell me, is there a manga where there is such a thing? I would really appreciate it if someone would respond.

Sono Mono. Nochi ni... (NARIIE Shinichirou) and This Time I Will Definitely Be Happy! has elements of this, but not really dark. Plus, in the second one, it's the girlfriend who gets left behind and loses her love.

~4400 manga completed
~1700 ongoing...