Ninja Defenders : Cat Shinobi

This is a challenging portrait-oriented tower defense game with a solo, intense gameplay loop that can be played in short, interruptible sessions. While it offers high replay value and a light story, progression is heavily gated by a brutal gacha system and pay-to-win mechanics, making it difficult to advance without spending money. It's best suited for players who enjoy strategic depth and don't mind a significant grind or potential paywall.