Kazumi Higashiyama (Heimdall)

Sent by Odin to assassinate Loki, the watchman. He devises clever plans, such as control over other beings or even mirages to taunt the opponent. It's believed that if he and Loki clashed they would both die as the myth in Ragnarok portrayed it, so a serious confrontation is avoided until the end of the series, in which Loki convinces him that he may have lost his eye but gained a friend, the falcon that accompanied him. He believes Loki to be the thief that stole his eye, so in addition to carrying out the assassination order, he intends to retrieve his eye or avenge its loss by any means necessary.

Even though "Kazumi Higashiyama" doesn't attend school, Heimdall still has a daily schedule consisting of piano lessons, singing lessons, and cram school. In the anime, Heimdall usually gets dragged along on shopping sprees by his roommate Freyr, much to his own dismay.

Appearance
Heimdall takes the form of a young boy as a disguise. However, due to the theft of his right eye, he is forced to have neck-length purple hair that completely covers the right side of his face.

His nails are actually long, sharp claws, so he wears bulky gloves to hide them

Personality
He is one of the more serious characters in the series, Heimdall is also the butt of many jokes. The manga frequently makes fun of his serious personality and his obsession with Loki.

Freyr
Freyr is Heimdallr's roommate and partner in assassinating Loki. Their initial plan is for Heimdall to trap Loki and Freyr will cast a rune on him which will unable Loki to return to Asgard but Freyr doesn't recognise Loki and casts a different rune which starts Heimdall's annoyance with his idiocy.

But the two seem friendly with each other since Heimdall always helps Freyr in shopping (even though he dislikes it) and participates in his plan on helping Mayura keep the Mystery Club.

Loki
Heimdall despises Loki because he believes that Loki stole his eye (but it was in Odin's order).

With his thirst for revenge he uses people that surrounds Loki to team up with him using his mind powers.

After sometime he stops doing so (when the Norns show up) so Odin gives Heimdall a reminder of why he hates Loki.

Even though they are enemies, Loki still tries to help Heimdall when he was about to die.

Mayura Daidouji
Heimdall saw how Loki cares for Mayura so he used her as bait for Loki to come to his traps, (In the zoo, casino etc.)

However he stops when Freyr starts to have feelings for Mayura.

Trivia

 * His name is very similar to Kinoshita's co-author in Tactics, Kazuko Higashiyama.


 * In the manga when Heimdall was about to literally stab Loki's eye out, Loki sucks evil from his right eye, which indicates that there is a hole in the right side of his face. (Which explains why he has long hair)