In 1493, Hatakeyama Masanaga tried to commit seppuku with the tanto, but couldn't cut deep enough into his stomach. He got angry and threw the tanto, which then pierced directly through a yagen (a stone mill for medicinal herbs), which is responsible for its name. Yagen gained the reputation of having a sharpness that would never harm its master.
Oda Nobunaga loved the tanto. It's said that it was burned down at the Honnō-ji Incident along with Nobunaga.
He is frequently referred to within the fandom as 兄貴 ("aniki", big brother) or ニキ ("niki") for short because of his masculinity.