Haruka Hosokawa is a member of the opposition team, Team Hoshishiro and nicknamed as "Lunatic Ice Sword". He is Haruki Hosokawa's younger twin brother and made his official appearance in chapter 19 of the manga like his brother. Haruka comes off as someone cold and detached from others, often bluntly displaying his contempt and disinterest. Although his aloof personality and blunt nature give off the impression of rudeness, Haruka remains genuine in his efforts to remain polite. Haruka is absurdly modest in regards to his own abilities, seeing himself was nothing special; though his following logic that everyone is just weak is enough to suggest a level of arrogance. Haruka harvests a jealousy of people who flourish in social settings, a stark contrast to his own unfriendliness.

Spoiler

Though Haruka remains distant to both those closely associated with him and not, another facet of his personality shines through in regards to his unyielding devotion to those few he does care for- namely his twin brother, Haruki. He tends to become oblivious to reality in close proximity to his brother, uncaring for any other interests outside of pursuing his brother’s attention. His affections cross the line into the obsessive, as he “practically worships” his brother. Although his love is genuine, his expression of adoration is shuttersome and without thought to others’ comfort- those witnessing his actions often left mildly unsettled, and those subjected directly left traumatized. There’s another side of Haruka’s love which is more subtle and tender than his usual brand of obsession- though the underlying qualities remain the same. Haruka blames himself for making Haruki quit playing survival games as he was the one who defeated his brother in the latter's second attempt at TGC. He apologises to his brother before stating that even if it is survival games, it is still Haruka's win.