Heartseed

Fūsen Kazura (ふうせんかずら) aka Heartseed, is the supernatural being that is responsible for the many phenomenons the Student Cultural Society face. When Heartseed appears, he is normally in possession of Gotou Ryuuzen's body, though he is not limited to possessing only Gotou and has proven capable of possessing others just as easily. Heartseed's mysterious powers leave the Cultural Club with little choice but to act as his entertainment, each time triggering a phenomenon for its members to overcome until Heartseed is satisfied.

Personality
Heartseed always talks with a slow, monotone voice as if tired, and when controlling others, his movements are similarly sluggish. In his quest to be entertained, Heartseed has proven willing to take extreme measures should he feel that, under the current conditions, the StuCS are not being interesting enough. Despite his seemingly sadistic fascination with the Cultural Club, he always refers to them politely and has stated he would never go as far as to kill someone for the sake of his entertainment, though whether or not his word can be trusted is debatable. Heartseed is also very secretive, only ever revealing what the club members need to know and never anything more.

Motive
A mysterious being, Heartseed claims that he wishes to be entertained. To that end, he observes Yamaboshi High's Cultural Club, just because he thought the members were "fascinating." Despite the ordeals he puts the StuCS through, he always seems faintly pleased when they do overcome his phenomenons. Heartseed has plagued other groups with phenomenons in the past, but the ones he had the most intimate and longest contact with was the StuCS. One reason for this is that compared to other people who experienced the phenomenons, the StuCS handled it without the group breaking a part. Usually when others have their personalities exchange, they last no longer than 2 weeks before their group collapse and the members are at their breaking point. This can be caused by the inability of one member to act as another or can cope with others calling by the name of the person's outer appearance. This was also seen in the Track and Field Club where they decided to trap themselves in their club room instead of living out their lives normally.

In Asu Random I Heartseed's motives are revealed to not only be for entertainment, but also to discover how to be human. He later rebels against No.3 by working with the StuCS to keep their memories of the phenomenons. From his more detailed explaination in Asu Random II, the phenomenons do not end because the StuCS are no longer interesting; they end once the group has become united in their thoughts and feelings about the phenomenon. An interpretation of this is that the phenomenons are not interesting anymore. In his final meeting with the StuCS, he told them that the Heartseeds are very similar to humans, but one thing they do not know how to do is change. As a result, Heartseed was very curious of the human potential for change and was drawn to the StuCS where he witnessed dramatic changes as its members matured into different people since his first observation.

Appearance
Heartseed has yet to appear himself in person, and that is assuming he even has a physical form. When he controls others, the possessed person's eyes always become droopy, as if tired, and their pupils lose their glow.

Phenomenons
Heartseed is shown to be a powerful supernatural presence capable of performing many mysterious feats such as and not limited to: Some of these abilities manifest in the form of phenomenons that occur at random and will continue until Heartseed deems he has been adequately entertained by how the characters respond to them. Heartseed also implies that the abilities he has demonstrated so far are just a sample of what he is capable of.
 * Switching people's minds.
 * Possessing others.
 * Manipulation of (or at least predicting) Survival Rates.
 * Forcing people to give into their impulses.
 * Allowing Telepathic Communication amongst individuals.
 * Allowing an individual to change the way others physically perceive them.
 * Allowing individuals to see the desires of others.
 * Though he has yet to demonstrate it, Heartseed has suggested he is capable of returning an individual to any point of their life in the past.

Other Abilities
When in control of others, Heartseed is capable of bestowing superhuman abilities to the body. For example, despite Gotou himself being a rather unimposing individual, while Heartseed is controlling him, he is able to effortlessly fend off attacks from Yui who is a karate expert. While controlling Gotou, he was also capable of jumping from the roof of the building to reach to the StuCS clubroom in order to secretly meet with the StuCS in Asu Random II.

Authority
Heartseed has full control over the phenomenons he causes, which is best seen during the Hito Random arc. Heartseed initiates the body-swapping phenomenon and has himself demonstrated the ability to possess the bodies of others without resistance. He can start and end the body-swapping process; however, he allows the body-swapping to randomly choose the candidates amongst the group as it will be more interesting. He is also capable of letting the candidates choose who they wish to body-swap with amongst themselves, but only when he allows it. It is also implied that even though he states all phenomenons are random, he purposefully chooses to activate some at a specific time to make things more interesting. It is implied that Heartseed holds authority over No.2 by being able to end his Time Regression phenomenon and having the ability to suspend No.2 if necessary.

No.2
Another mysterious factor of Heartseed is that there are apparently several beings like him, such as No.2, who seemingly acts on an agenda different from Heartseed's. No.2 initiates the Time Regression phenomenon during the Kako Random arc but was temporarily neutralized by Heartseed for overstepping his boundaries. Despite possessing similar powers and mannerisms, the two state to be independent from each other and as such, No.2's true motives and relationship with Heartseed are shrouded in mystery.

No. 2 later reappears during the Asu Random I arc where he states to be interested in Heartseed's relationship with the StuCS. In Asu Random II, No. 2 assisted the StuCS by providing them with important information.

No.3
A third Heartseed-like sentient appears in Asu Random I and applies a variety of phenomenons to the other students of Yamaboshi High. There appeared to be more than one of No. 3 since it is always referred as a group of No. 3's in the novel. He usually possesses first year students and is responsible for sending the entire student body, minus the teachers and third years, to the "Isolation Dimension." No. 3 is also responsible for attempting to wipe the memory of Heartseed and the members of StuCS using Records Deletion. He is an enemy of StuCS and Heartseed. He uses the body of an unnamed first year student.

Trivia

 * Heartseed's name refers to Cardiospermum, a type of vine plant that produces sack-like seedpods. The seeds have distinctly heart-like indentions.
 * In the manga adaption, Heartseed is depicted as slightly more lively than he appears in other media, even smiling on occasion.
 * In the "language of flower" (花言葉), the Heartseed plant means "Always together with you" and "Want to depart with you."