He possessed his ex-girlfriend's only son.

The previous title was misleading, so I changed it.

Old Title: 『When I Woke Up, I Had Become My Former Lover's Son —After Leveraging My Professional Experience to Resolve Troublesome Issues, I Found Myself Constantly Bothered by the School's Most Beautiful Girl—』

I broke up with my former lover during my first year of high school. Though I dreamt of our reunion, the opportunity never arose, and before I knew it, two decades had passed.

Our reunion arrived in a form we never wished for.