The "Walkthrough" part of the search query is crucial. While the game presents itself as a linear story, it is packed with .

: This path involves pivotal early decisions. Key interactions include meetings and specific scenes in the MC's room that can trigger jealousy or further dialogue with other characters like Natsume.

This unlocks the epilogue where the "Eternity" in the title is explained—a promise kept across timelines.

To unlock the true "Extra Life," you must first trigger a specific, obscure failure state: