GASSAN SADAYOSHI(月山貞吉) was born in Dewa province but worked in Settsu province. He was a descendant of the Gassan school(月山派).
- Gassan Sadayoshi larned swordmaking from his father Okuyama Yasaburo Sadachika(奥山弥三郎貞近) and moved to the Edo city at the age of 20 to become an apprentice of Suishinshi Masahide.
- After learning from his teacher in Edo city he moved to Settsu province in 1833 and revived the GASSAN SCHOOL(月山派) there. The school continues until today.
- In 1843, He adopted Gassan Sadakatsu. Most of his very later works were made by his adopted son.