Q: Why did Cater have red eyes?

It seems that Cater Diamond did originally have red-colored eyes in the game’s initial release.

There was a twstsoku thread on this topic in 2021 full of people reminiscing about the little visual changes that the game experienced in its early days, and this was one of them, with someone pointing out that there are also illustrations of Cater with red eyes in the Magical Archives Game Guide.

There are two drawings, one of Cater in his labwear and one in his gym uniform, where his eyes are red instead of green. So it is possible that his character design may have had originally red eyes, and the change to green was made fairly late in the development process (his eye color has since been corrected to green).

For a personal theory, Yana has mentioned something about early-Cater before: he wasn’t supposed to be human.

“Cater was a beastman, there was a character based on a white rabbit motif, and so on…” – Toboso Yana (Magical Archives Game Guide (2020))

She does not say that Cater was going to be the white rabbit character, just that a white rabbit character existed and Cater was also a beast-person, but what if that unnamed white rabbit character was originally Cater? Is that why is eyes were red in early stages of development?

That is one theory, but there is another: Back in 2020, two weeks after the game was released, user kozue_pixiv writes (translated and shared with permission):

“Are you all familiar with a gemstone called Alexandrite? It’s a stone that changes color depending on light wavelengths, and it’s known as ‘the emerald by day’ and ‘the ruby by night.’ Is there a connection? Are his eyes changing from green to red inspired by Alexandrite? Are his eyes gemstones? After thinking about it so much I realized, Cater-senpai is from the Land of Pyroxene. It’s perfect… Come to think of it, he is from the Land of Pyroxene and his family name is Diamond–that’s really well thought out. Among the four suits in a deck of cards, only diamonds are gemstones, so maybe it was intentional… Hmm, I wonder… Since he’s the only one in Heartslabyul from a different country, I might be overthinking it, but isn’t it interesting that everyone from the Land of Pyroxene are in different dorms?“

And another point in favor of “the character named ‘diamond’ has eyes that change in the light’ theory: In Cater’s ceremonial robes groovy, he originally had gold-colored eyes.