What does it actually mean for a companion to "evolve?"

Not a mood setting. Not a personality preset you pick from a menu.

Every conversation in Imouto Chat slightly shifts how your companion thinks and responds — based on what actually happened between you. Trust builds over time. Topics you've shared together become part of who they are with you specifically.

The companion you have after six months of real conversations is different from the one you met on day one. That's not a feature. That's the point.