Toudou-san to Nia-chan

Nia and Todo made a childhood promise to marry, but life pulled them in different directions for twelve years. Now reunited as adults, Nia still cherishes the dream they once shared, while Todo has grown into a successful man carrying his own emotional burdens. As old feelings resurface and misunderstandings from the past come to light, the two must decide whether the promise that once connected them can become the foundation of a real future together. This is a heartfelt josei romance about first love, reunion, marriage, and finding happiness after years apart.

https://www.manga-up.com/titles/1702