Saku Saku has 5 endings/routes, for 5 different heroines (Ann, Mio, Yuri, Konami, Tina). You’ll only need one save slot, and will unlock all the CGs in the process. This guide is for both the adult & steam versions of the game, but the subpages containing route screenshots are from the adult version of the game. *This walkthrough is based on the link below. However, the screenshots have all been provided by myself ;-)
Saku Saku: Love Blooms with the Cherry Blossoms Walkthrough (Sekai Project / Denpasoft) - Otaku Lair
Only available after finishing Ann’s route