The story
Credit Saison was founded in 1946 as Midoriya (緑屋) by Torajiro Okamoto. It was originally an operator of department stores specialized in installment selling.
Seibu Retailing Group, one of the (now former) subsidiaries of Seibu Railway, purchased Midoriya in 1976, attempting to add financial services to its portfolio of customer services. Midoriya's retailing division was transferred to Seibu Department Stores, and Midoriya itself was renamed Seibu Credit (西武クレジット, Seibu Kurejitto) retaining the credit management division.
Seibu Railway spun off Seibu Retailing in 1983 and Seibu Retailing was rebranded as Saison Group. Seibu Credit issued the first Saison Card in 1983. Seibu Credit finally rebranded itself as Credit Saison in 1989, standing as one of the Big Five core businesses of Saison Group.
Following the collapse of the Japanese asset price bubble in the 1990s, Saison Group fell into financial difficulties. The group's longtime president Seiji Tsutsumi was expelled from management in 1991. The group's creditors including Dai-Ichi Kangyo Bank and Industrial Bank of Japan (now part of Mizuho Financial) pressed the group to restructure its business. Credit Saison parted from other retailers of Saison Group, and formed an alliance with Mizuho in early 2000s.
From Wikipedia’s article on Credit Saison, shared under CC BY-SA 4.0.5