Here's an interesting one for you. This week's Famitsu includes an interview with NieR: Automata creator Yoko Taro and Undertale creator Toby Fox. In the interview, Fox has Taro talk about how he heard about Undertale, and what he thought of the game.
Toby Fox: When did you first find out about Undertale, Yoko-san?
Yoko Taro: I found it from an overseas fan who suggested it around the time it was only available as a demo, saying “There’s this game that I think Yoko would really like.” So when I actually played the demo, I was like, “Oh, I… think this is fun, but it’s the kind of game I can’t truly enjoy without understanding the English details,” so I decided to wait for it to get localized.
Toby Fox: So how was it when you got to play it? Did you like it?
Yoko Taro: I thought it was very amusing.