Side Effect

Side Effects are extensions of human abilities which manifest in people with high amounts of Trion due to the effect of trion on the brain and sensory organs. There are two types of Side Effect Holders, those who have the ability from birth, and those who later acquired it due to an external factor, however the specific condition to manifest one is unknown, and are rare overall.

Border has a makeshift ranking system depending on the rarity, but the rank doesn't equal strength, for example Kikuchihara was able to improve Kazama Squad thanks to his enhanced hearing despite being the lowest rank of C.
 * S - Extrasensory Perception, like Jin's Foresight.
 * A - Superhuman Ability, like Yōtarō's ability to talk to animals.
 * B - Special Constitution, like Kageura's Emotion Perception and Murakami's Enhanced Sleep Learning.
 * C - Enhanced Senses, like Kikuchihara's Enhanced Hearing.

Usage
Due to the nature of Side Effects, many holders use their ability in combat, but there are multiple cases where it can be used outside of combat, although there are cases where the holder use their ability either purposely or accidentally without knowing it is a side effect.

Side Effect Holders

 * Yūichi Jin - Foresight, which lets him see the future of those before him.
 * Yūma Kuga and Yūgo Kuga - Seeing Through Lies (をく), which lets him see the lies of others through a visual cue.
 * Chika Amatori: Sensing enemies and Erasing Presence (・をす), Chika is the only known person who has 2 side effects, the latter lets her erase her presence, at the cost of needing to focus heavily, while the former lets her detect neighbors and trion soldiers, but not much is known about both side effects.
 * Yōtarō Rindō - Talking to animals (との) which lets him talk to animals, however how intelligence of the animal will determine the response.
 * Shirō Kikuchihara - Enhanced hearing, which not only increases his hearing by 5 or 6 times, it increases the precision by a lot.
 * Kō Murakami - Enhanced Sleep Learning, which enhances stabilization and consolidation of memory during sleep.
 * Masato Kageura - Emotion Perception, which lets him receive emotions aimed at him from other people
 * Tsukihiko Amō - Name Unknown, but it lets him View others' fighting ability as colors.
 * Yomi - Perfect Parallel Processing, which allows him to multi-task at maximum efficiency.

Trivia

 * A recurring theme in the series sees Side Effects contributing to their possessor's misery:
 * Chika's Side Effects allowed her to escape capture at the hands of Trion Soldiers for years, and are thus indirectly responsible for her feelings of guilt after her friend was abducted;
 * Following his father's death, Yūma's Side Effect allowed him to see through the empty platitudes and attempts at manipulation of the people who surrounded him, some of whom would have preferred his father to survive rather than him.
 * Jin's ability to see the future comes with great responsibility, as he may be forced with the choice of letting someone be injured or even die to prevent a worse outcome.
 * Kikuchihara was mocked for the supposed inutility of his Side Effect, with it causing him to overhear himself being mocked.
 * Murakami lost friends due to his Side Effect allowing him to surpass them in their favorite activities in a short time, causing the group to disintegrate.
 * Kageura is not only privy to others' negative feelings towards him, but the prickling sensation provoked by his Side Effect is all the more unpleasant if the emotion directed at him is a negative one.