At his time at the studio, Ōsaka worked with numerous noted animators, including Kazuaki Mōri, Masahiro Kase, Tōru Yoshida, Hiroyuki Okiura and Kazuchika Kise, many of whom who went on to found Production I.G, and also supervised Takahiro Kimura.
Ōsaka, along with fellow animator Toshihiro Kawamoto and producer Masahiko Minami, co-founded the studio Bones in 1998.
An anime fan, he had wanted to be an animator since his high school days, being inspired by Sunrise's iconic 1979 series Mobile Suit Gundam and the works of the manga artist Mitsuru Adachi.
During the spring of 2007, Ōsaka's health had deteriorated and spent his remaining days in his hometown of Neyagawa, Osaka Prefecture, where he had been staying at his family residence.
His death was reported on several news outlets, including the blogs of his animator colleagues and major national newspapers, with numerous fans paying condolences.