Asai

Asai (浅井) is a member of the Kouga School of Ninjutsu.

Background
Asai's background is largely unknown, but they were apparently trained alongside Sakata, Yasu, and Tsurigane Saryou when she was still with the Kouga.

Asai remained in the service of the Kouga with the others while Tsurigane went undercover as a Child Error in Academy City. By the later months of the story's first year, with the Kouga reaching their limits in the changing times, they sought to acquire new methods and abilities to contend with the likes of Academy City and Baggage City, which would result in Asai, Sakata and Yasu going on at least two missions to that end, under Oumi Shuri's lead.

Baggage City Arc
In mid-November, Asai, Sakata, Yasu, and Oumi Shuri, went to Baggage City for the Natural Selector tournament in order to find an interesting person that they could get and analyze their abilities for the sake of the Kouga School.

Asai, Sakata, and Yasu later come upon Kihara Enshuu, while Shuri contacts them regarding a treasure she found fit for the Kouga, though only their screams reach their ears, as they describe her as a monster. They are presumably killed by Enshuu.

Jailbreaker Arc
Asai was part of the Kouga group led by Oumi Shuri, together with Sakata and Yasu, who infiltrated Academy City in mid-October with Tsurigane's help to learn what they could in the city for the Kouga, and subsequently participated in the Jailbreak Trial two days later on Tsurigane's suggestion (actually to aid her city friends in breaking out Shundan Kimi).

During the event, they scaled the outer walls, over the top around the time that other competitors had opened a hole in the wall below, and once inside the grounds, fought off the guard robots with their respective ninjutsu. Inside the prison building, the group split up, reuniting a little while later after Oumi took a painful blow to her rear end, shortly before the event concluded.

When Tsurigane was defeated by Shirai Kuroko after openly betraying the Kouga, Asai and the other ninjas observed the events from a nearby rooftop. After hearing from Oumi about how the Dark May Project had affected Tsurigane and it had proved the risk of incorporating Academy City's technology into their ninjutsu, Asai acknowledged Oumi's declaration that Tsurigane's judgment would be left to the city's laws and that its technology was not to be touched again, before the group departed.

Abilities
Being a Kouga ninja, Asai was trained in their techniques since early childhood. His combined ninjutsu and athletic abilities were sufficient to traverse the Second Reformatory's outer defenses, scale the outer wall and fend off the facility's guard robots during the Jailbreak Trial.