A full save requires purposefully failing certain encounters. Most scenes are tied to specific locations (train, alleyways, etc.) or specific enemy types.

To reach a full save state, you must navigate both the main story path and the optional "defeat" scenes. :

If you prefer to earn your progress, here are a few tips to help you reach that 100% mark on your own:

Check the "Gallery" or "Load Game" menu to ensure the 100% completion has registered. Mastering the Game (Without a Save File)

If "Chikan Undercover Agent Rina Full Save" refers to a game, anime, manga, or another form of media, here is some general information that might be relevant:

: Multiple tiers of interactions based on crowd density. The Park/Alley : Evening-specific events.