I've noticed this's probably one of my favorite motifs in fantasy and adventure series. Tokyo Underground, Flame of Recca, Elemental Gelade, Crime Edge, R2, and so many others. While there's plenty of similarities and differences, one thing all have in common is that the number one core point of the story, the hero's main driving force, is to save and/or protect one young girl. The girl may take part in combat in one way or another, there's nothing stopping her from being an awesome fighter herself, but the core remains the same: some force or forces seek to harm her or take her away, and protecting her becomes the hero's number one purpose. 653da

Try Chounin A wa Akuyaku Reijou wo Doushitemo Sukuitai

~4400 manga completed
~1700 ongoing...

Try Kanojo o Mamoru 51 no Houhou.

Or maybe Dance in the Vampire Bund. It has a fairly complex plot with a lot of different moving parts but the ML's main motivation is always to protect the girl he loves.

"We can not resort to simplistic or extreme solutions which substitute myths for common sense." ― Jimmy Carter