The remake version of ToHeart features two helpful functions—Route Guide and Decision Support—so I believe you won't need to deliberately seek walkthroughs to fully clear the entire visual novel.

However, the game features two heroines whose routes unlock only after completing specific other heroines' storylines.

Therefore, I've written this guide outlining the unlock conditions for the storylines of these two heroines, hoping it will be of some help.

Rio Hinayama: Unlockable after completing Akari Kamigishi's route.

Ayaka Kurusugawa: Unlockable after completing Serika Kurusugawa and Aoi Matsubara's routes.
Note: Before reading this storyline, I highly recommend enabling both the Route Guide and Decision Support features first. Alternatively, you may also refer to the relevant guides.
Otherwise, you might enter the scene where you "affirmed your friendship with Masashi" and waste time unnecessarily.

May your ToHeart journey gently unfurl the precious memories tucked away in the corners of your heart.