Nagi Hikaru - My Ex-boyfriend- Who I Hate- Make...

While there isn't a widely documented manga exactly titled "Nagi Hikaru - My Ex-Boyfriend- Who I Hate," this sounds like a mix of several popular titles involving these specific characters or themes. Below are "solid reviews" for the most likely matches based on your description: The Summer Hikaru Died (Hikaru ga Shinda Natsu)

“The things he made me feel: Small. Loud. Forgotten. Too much.”

If you are writing your own version of Nagi Hikaru, My Ex-Boyfriend Who I Hate - Make Him Regret Forever , here is the classic 5-act structure that guarantees emotional payoff. Nagi Hikaru - My Ex-Boyfriend- Who I Hate- Make...

Understanding the "Enemies to Lovers" Phenomenon in Modern Romance Fiction

The tension isn't just awkward; it is electric. Every argument feels like a battle, and every moment of forced closeness feels dangerous. While there isn't a widely documented manga exactly

Let that be the only revenge that matters.

Here's a full review:

For the first six months after the breakup, hatred was all that kept me alive. I hated his perfect hair and his condescending voice. I hated how he posted photos of his new girlfriend (Yuna, of course — the “friend”) just two weeks after leaving me. I hated that he looked happy. I hated that I had loved someone so incapable of love.