Masculine Girl, Feminine Boy: Although Marin is not entirely masculine, she seems so next to the very feminine and girlish Haruhi; it helps that Marin used to be very boyish (complete with boyish haircut) as a child. Ryuu lampshades this.
NaÔve Newcomer: Marin has no idea where to go the first day sheís at school. If youíre not paying attention, she also forgets her class number.
Keet: Ryuu never seems to run out of energy or smiles.
Lethal Chef: When Marin tastes the bento that Ryuu made, she notes that the meat is overseasoned, undercooked and practically raw. On the contrary, Ryuu thinks itís delicious.
Man Child: Ryuu has a few of these tendencies, such as his enthusiasm at getting to play in the rain or ride the swings at the park. His excuse is that he never got to do those things as a kid because he was either at home or in the hospital.
No Sense of Personal Space: Ryuu has just met Marin, but heís very friendly and never misses a chance to tease her about being romantically involved or get physically close to her in some way.
Power at a Price: The reason why Ryuu faints so much is because he does not have enough energy to teleport as often as he would like due to his heart condition.
Sincerity Mode: When he confesses to Marin, she doesn't take him seriously at first, assuming that he sees her as just another conquest. It isn't until later that she realizes how much he cares.
Stepford Smiler: He's very good at hiding his insecurities and health problems underneath his carefree disposition. It's most noticeable when he forces himself to smile after Marin initially rejects his love confession.
Big Brother Instinct: Lucan has four younger sisters, so taking care of Marin comes naturally to him.
Big Man on Campus: Lucanís the most popular guy in school, has his own Unwanted Harem and definitely qualifies as one of The Beautiful Elite. It's deconstructed on his route when it's revealed that he's actually terribly insecure, and the main reason he's so popular is that he unconsciously brainwashed the girls around him into loving him out of fear of being alone.
Bishōnen/Pretty Boy: More so because of his slightly longer hair and his acknowledged pretty boy looks in-universe.
Nice Guy: He's consistently sweet, awkward, and an overall gentleman towards Marin. Unless Marin rejects him after she learns about his dark secret. Then he becomes not so niceanymore.
Not Good with Rejection/Yandere: If Marin rejects Lucan after she learns about his unintentional brainwashing of multiple girls, he intentionally brainwashes her into forgetting this and becoming as mindlessly devoted to him as his fangirls. Marin's profile even gains Mind-Control Eyes after he does this. Brrr.
Childhood Friend Romance: Of the unrequited kind. Haruhi has feelings for Marin, but he hasnít confessed them and she doesnít seem to feel the same way about him. That is, unless you choose him over Kaius.
He Is All Grown Up: When Marin is expelled from Planets and returns home, she finds that Haruhi has finally hit puberty and has adopted a boyish image.