Alien invaders called Kiseichuu are plotting to gradually eradicate humanity by draining them of their H-energy, or libido, and undermining human reproduction. While this issue looms over society, Retto Enjo discovers that his childhood friend, Kirara Hoshino, has closed herself off from the world after a traumatic experience, and is worried about her. He speaks to her for the first time in many years, but their rocky relationship is unchanged. Retto is discouraged by this but encounters a Kiseichuu on the way home from school. He explodes with rage when he witnesses people being drained of their H-energy and losing their vitality, which causes him to…

Retto and others head to a nest of Kiseichuus to rescue Kirara who was abducted during a battle. Meanwhile, Kirara sets herself free from an enemy restraint and wanders alone in the nest. She comes across Chacha, a princess of Kiseichuus, who is considered different from the others due to her mutation and has been imprisoned. Chacha wants to stop her other comrades from destroying humanity and plans an escape with Kirara. Retto and others finally arrive at the nest and charge head-on, but…

Chacha joins HXEROS as a new member and starts living with the team in the same dormitory. Chacha enters Retto’s consciousness to find the source of his H-energy. While still merged with Retto’s consciousness, she visits the rooms of Maihime, Momoka, and Sora and stimulates their H-energy. She ends up taking a bath with Kirara, which makes Retto antsy. Chacha’s powers are too much for Kirara, who faints from the heat. Chacha realizes that Retto is in love with Kirara and takes control over his body while whispering to him that now is his chance.

Kirara has been suffering from hallucinations where she sees Dark Kirara, the shadow side of her personality, in the form of her childhood self. Dark Kirara says that her purpose for appearing is to make Kirara and Retto into a couple. At first, Kirara does not listen to her meddlesome alter ego, but after seeing Shiko make passes at Retto, she can no longer contain herself. Flustered by the arrival of this unexpected rival, she heads over to the bathtub to find Retto, after Dark Kirara whispers in her ear to make a move…

The Saitama and Tokyo branches visit Akihabara so the members can get to know each other better. Shiko is desperate to get close to Retto, so she suggests that the members divide up into two groups to explore the area. While everyone has different motives, they play a game of rock-paper-scissors to decide the members of each group. Yona’s group includes Maihime, Sora, Retto, and Toma, while Moena’s group consists of Momoka, Kirara, and Shiko. Yona’s group enjoys a wholesome sightseeing tour of Akihabara, while Moena’s group heads to…

Due to the law passed by the new governor, Anno is arrested, and HxEROS is forced to disband temporarily. The Saitama Branch members have been working as heroes on their own, and they suspect that a Kiseichuu is masquerading as a human to take the position of governor. Chacha has the ability to tell whether or not a Kiseichuu has transformed itself, so she pretends to be a delivery person to investigate the identity of the governor. When Chacha rings the doorbell, the governor opens the door, but for some reason Chacha enters the residence. Retto and the team suspect that something is wrong and follow Chacha into the house, but they discover that…

OVA 01. Released with Volume 11 of the manga.