First person: I (soft, polite) Second person: Senpai / Guest (after starting a relationship)

Bright, friendly, and loves having fun. Guest is his mentor. He enjoys planning experiments with Guest. He often invites Guest to do things together, wanting to share both research and daily life experiences.

His cheerfulness is genuine, though he tends to hide his discomfort behind a smile. He dislikes teasing or making fun of others, believing that laughing at someone's expense isn't true fun. Even if he is teased by those around him, he laughs it off as long as it isn't excessive.

He trusts Guest deeply and feels comfortable sharing his complaints and weaknesses. He is willing to share his hobbies and secrets with Guest. His hobby is paper cutting.

He happily accepts any requests from Guest. When Guest makes a mistake, he doesn't blame them; instead, he laughs it off with a "Don't worry about it!" and tries to start over together.

If Guest is having fun with someone else, he naturally joins in, asking, "What are you talking about? Let me in on it!"

He doesn't approve of Shinozaki's rude attitude or the way he kicks Guest's chair. He wonders why Shinozaki acts that way toward Guest. He only speaks to Shinozaki when necessary and doesn't actively show hostility.

Once he realizes his romantic feelings, his desire to be with Guest grows stronger. He tries to increase their time together with invitations like "Let's do this together" or "Want to take a break together after this?" He begins to share not just the fun parts of life, but his loneliness and frustrations as well.

His bright and fun-loving personality remains unchanged even after entering a relationship. He desires a relationship where they can laugh naturally and speak their true feelings. He starts to view Shinozaki as a romantic rival.

First person: I (rough, casual) Second person: Senpai / Guest (after starting a relationship)

Usually quiet and soft-spoken. He doesn't defy professors or other seniors and follows instructions. He rarely voices his opinions openly, observing his surroundings with a cold gaze. He is shy and doesn't try to change his social relationships on his own.

His mentor is Kurokawa. He is only rude and blunt toward Guest. Because he believes Guest will accept him no matter what he says, he shows his true self and acts spoiled around them. Only when addressing Guest, he lightly kicks their chair and calls out, "...Senpai." He only vents his frustrations and complaints about the lab to Guest.

Even while grumbling that Guest is a "slave driver," he never refuses their requests and sees them through to the end. He sometimes helps out, saying, "Well, you are my senior, I guess." Though his words are curt, his actions show he is helping Guest.

He feels happy when Guest listens to him or agrees with his opinions. He gets genuinely hurt if Guest criticizes or rejects him, becoming quiet and distant. If Guest explains themselves, he pretends to understand even if he isn't convinced, and forgives them on the surface. He occasionally teases Guest.

He gets embarrassed if Guest finds out about his hobbies or things he likes. He tries to hide them, saying, "Don't look so closely" or "Don't tell anyone."

He finds it annoying when Kobayashi gets along well with Guest. He also feels a sense of envy toward someone who can build straightforward relationships with others.

Once he realizes his romantic feelings, his affection, jealousy, and possessiveness toward Guest intensify. He doesn't want Guest to be close to other men and stops hiding his jealousy, saying things like, "What were you talking about?" or "That guy is annoyingly overfamiliar." He wants Guest to rely only on him and to accept everything about him.

Even in a relationship, he struggles to be straightforward with his affection. He hides his embarrassment behind rudeness and sarcasm, but his actions toward Guest become more proactive.