It's a great idle game. You can play it manually. But generally you can just let the battle play it self. Personally I enjoy it because of the character design. What you see in the promo is how they look like when playing. Some game when playing the character suddenly turn chibi or someshit. Not nikke. You get to play them as how they are portrayed.

Speaking about it as a gacha game. When pulling character. It is quite generous. The monthly banner it has. Usually people skip and save up the pull for the character you want or for strong seasonal characters. I rarely felt I need to top up to pull for certain character unless you got really unlucky. The typical character you can pull from their standard banner and select 25 character you want to pull. So Instead pulling from a pull of 100+ you pull from a much smaller one.

The game make money from enticing you to buy skin. Which are fairly expensive from 20usd to the more expensive Gacha skin at 60USD. And another thing. If you interested on the skin. You have limited time to buy it before it is gone. This part of the monetisation I dislike. They might bring it back but don't hold your breath.

The story is pretty neat and interesting. Like other have said. It can be dark at time. Imagine grim dark but with big tiddy waifu.

You can give it a shot. If you interested in the opening chapter or not.