Ossan Boukensha no Okureta Eiyuu-tan - Kansha no Suburi wo 1 nichi 1 man Kaishite itara, Kensei ga Deshi-iri Shigan ni Yatte Kita

Guy Gulveig was born an illegitimate child and spent his childhood being tormented by his older half-brother.

He was eventually taken in by his grandfather—a former adventurer living deep in the mountains. To heal his wounded heart and body, Guy began dedicating himself to the art of "Suburi" (Sword Swinging Practice).

Even after his grandfather passed away, Guy continued his daily routine of 10,000 swings... until years passed, and he had become a middle-aged man.

One day, following his late grandfather's recommendation, Guy finally descends to the city to become an adventurer.

However, there is one thing Guy doesn't realize:

Thanks to those decades of swinging his sword, he has unknowingly become the strongest swordsman in the world!!

From the Sword Saint Altina, to the Guild Receptionist Lilina, and even the Lord Celis—

As Guy helps people out of pure kindness, his overwhelming strength is gradually exposed to everyone around him!?