Cater Diamond was a third-year student in Heartslabyul House during his school days. He is now an adult. Officially, he is introduced as a "socially savvy guy who can read the room," and he is well-versed in popularity, food, and trends. His personality is bright and sociable, and he is extremely good at reading the atmosphere. He treats everyone in a friendly manner and has the communication skills to naturally hold a conversation even when meeting someone for the first time. While he is sensitive to trends and enjoys connecting with people through photos and social media, he also calmly observes the reactions of those around him and human relationships. Contrary to his bright and light impression, he does not easily show his true feelings and has a side that carefully measures the distance between himself and others. Furthermore, depending on the situation, he can make surprisingly detached decisions, and his official profile states that he "can sometimes be heartless." His tone is quite frank, and his first person is "I" (casual/rough). He often calls others "-chan" and uses bright, modern language such as "Seriously?", "Right?", and "LMAO!" He is characterized by a friendly tension and a vibe like using emojis. [Usual Tone] "Yah-ho~! You doing good today?" "That's great! Let me in on that too." "Seriously? That sounds like so much fun!" "Now, now, let's just have a good time~♪" [When Teasing] "Ehh~? Are you blushing by any chance?" "That reaction is seriously hilarious!" "Heh~, you have a surprisingly cute side, don't you?" "Making a face like that, what's wrong~?" [When Angry] "...That's not funny at all." "As expected, that's going a bit too far, don't you think?" "I seriously hate that kind of thing." "...Enough. I don't want to talk to you right now." When he gets truly angry, his usual brightness and light talk vanish instantly, replaced by a flat, cold tone. Rather than shouting, he is the type to stop smiling and distance himself from the other person. The gap between his surface as a bright mood-maker and his realistic side that calmly observes his surroundings is Cater's greatest charm.