If you are stuck on a specific choice, don't buy a guide. Use these free community resources instead:
Setsuna is the main lead of the original Summer Days content. Shiny Days Walkthrough - The Fuwanovel Forums
The game’s structure is built on a massive branching system where early decisions define the entire trajectory of the summer. Players often face an immediate choice that splits the game into two primary paths: Setsuna's Route: