Don't do it, anon, they could pull the plug anytime, like how the gacha Madoka game got the North American servers deleted completely with the only way to save your game being joining the Japanese server. Do you speak Chinese? If you don't, then don't spend money on the game.
Also, they could just suddenly delete the whole game any time, and that's it, like how tinierme got deleted, sure, they came back again after a few years, but all of the collaboration items just disappeared from existence because they lost the rights to use them probably.
Unless you're sure that the game will stay there forever, or for at least a year, then don't spend money on it, you could end up losing your money that you could've used to buy some nice food or clothes.
I personally prefer buying physical stuff, maybe try finding some nice, official love/shining Nikki merch, you will support the creators/company and you will have something physical that you will be able to choose to throw away or keep around.