Subaru is the head of the Sumeragi Clan of onmyouji at the young age of sixteen, and is intensely dedicated to his work. Despite this heavy burden, he remains a sweet, naive boy who is devoted to helping those in need.He is very close to his twin sister Hokuto, and often relies on her for emotional support. He is easily flustered by Seishirou's grand romantic gestures toward him, but holds a great respect for the man, and gradually grows to rely on his support as well.Some tropes that apply to Subaru:
Friend to All Living Things: Subaru loves animals, and often bonds with Seishirou over the animals at his practice. He yearns to go to college to be a zookeeper — however, his duties as clan head have made that dream all but impossible.This seems to be on purpose to go with his hardened demeanor after he got older and more depressed.
Nice Hat: A constant feature of the outfits created for him by Hokuto.
Onmyodo: A practitioner and child prodigy, and comes from a long line of fellow onmyouji.
Parental Abandonment: His only shown relative is his grandmother, who lives in Kyoto. Subaru and Hokuto live on their own in Tokyo.
Theme Naming: Like Hokuto and Seishirou, Subaru is named after a constellation — "subaru" is the Japanese term for the Pleiades.
Incidental Meaningful Name: Later on in X1999, it is revealed Subaru is one of the Seven Seals - each Seal being born under stars in the Pleiades. Both he (and Hokuto, being his twin) were born under the "north star" - but the literal name went to "Hokuto," who was born first. (See her section for more.)
Waif Prophet: Subverted. Though Subaru looks waifish and mild, he is a combat-trained black belt. In volume six, he nearly breaks the arm of some punk who was harassing a blind man, and scares off the rest of the punk's friends with a look.
His stature is pretty slight, but his main problem is that he often just doesn't take care of himself (such as forgetting to eat), particularly when he gets really busy (which is all the time).
Yaoi Guys: With Seishirou, much to his embarrassment.
Shotacon: Seishiro's first meeting with him under the sakura and consequential "friendship," "love," and badtouches.
Hokuto is Subaru's elder twin sister, and his loyal emotional support. She is a happy, energetic young woman, and incredibly skilled with her sewing machine. She is nowhere near as skilled as Subaru at magic, but makes up for it with perseverance (and a healthy dose of martial arts).She wishes only the best for her younger brother, but fears that his tender heart will only bring him pain. She eagerly encourages Seishirou and Subaru's relationship, hoping to make Subaru care about his own needs and feelings. Despite this, she often senses something just a little off about Seishirou...Some tropes that apply to Hokuto:
Ambiguously Gay: She and the girl she rescued in the "Smile" side-story grew awful close. She even refers to "going on a date with her girlfriend" in a later arc.
Theme Naming: Like Subaru and Seishirou, Hokuto is named after a constellation — "hokuto" is the Japanese term for Polaris.
Incidental Meaningful Name: Both she and Subaru were born under the north star, so the name could have been given to either of them - but she was born first, and therefore was "the guide." There's more to them being born under a constellation; see Subaru's section for more.
Seishirou is a friend of the Sumeragi twins; a warm, kind veterinarian in his mid-twenties. He likes to goof about with Hokuto, and constantly expresses his romantic intentions towards Subaru, to the latter's embarrassment. Despite his playful demeanor, he is a knowledgeable mentor to the twins, and often gives sobering commentary on the state of Tokyo and human nature.Hokuto suspects him of being the Sakurazukamori, the longtime rival of the Sumeragi clan — Seishirou always laughs the accusations off, as he, of course, has no magic ability...or does he? He does, and is. His powers as an onmyouji surpass Subaru's, and he has far fewer compunctions about using them to hurt others. Over the course of the series, his true nature (and the connections he has to Subaru's foggy memories of a meeting under a cherry tree) slowly comes to light.Some tropes that apply to Seishirou:
Friend to All Living Things: He is a kind and caring doctor to all the animals in his care, and often bonds with Subaru over their shared love of animals. This and the trope itself is all a deliberate act on Seishirou's part. He uses some of the animals in his care as sacrificial decoys to deflect the negative splashback that his magic would otherwise cause on him.
Kick the Dog: Seishirou uses his veterinary practice for magical purposes - the backlash of his spells strike the animals instead of himself, often killing them.
Also, just as Subaru realizes his love for Seishirou, the latter beats him to a pulp. He simultaneously explains, while breaking Subaru's arm and kicking him around the room, that despite his previous assurances of love he really feels nothing for anyone.
Milky White Eyes: After his eye is injured. It's never clarified if his eye is totally missing and thus he wears a glass eye, or merely blinded to the point of being discolored. But more than likely it's merely blinded: in X1999 after Fuuma stabs Subaru in the same eye, after his bandage is removed, we see the same white blankness.
Memetic Molester — thanks to a certain annex and his tendency to be... well, Seishiro.
Onmyodo: As expected of the Sakurazukamori, and is more powerful even than Subaru and his grandmother.
Secret Identity: Seishirou as the Sakurazukamori, though it was fairly obvious from the beginning.
Stalker with a Crush: He certainly is very touchy-feely with Subaru, and always knows where he happens to be, and always leaps to his protection. He does literally spy on him constantly with onmyoujutsu, and grows increasingly possessive of him. Of course, he still claims he feels nothing toward him.
What Is This Thing You Call Love?: Seishirou, as a sociopath, literally cannot comprehend normal human emotion. The bet he made with a young Subaru long ago was to see whether he could be made to love someone, and Seishirou claims Subaru failed. Claims.
Born Lucky: Horrifyingly deconstructed, as he weaponizes his extremely good luck to stage accidents where he will as much get broken limbs, but his targets will die. This is how he killed both Kazumi's brother and his own boss.