Kei Tachikawa

Kei Tachikawa''' is the A Class leader of Tachikawa Unit and Ranked #1 attacker. Due to his actions, he is an antagonist of the Black Trigger Retrieval Arc.'''

Appearance
Tachikawa has medium length brown hair. Usually he wears black trousers and a jacket, but in the trigger mode he wears a long black jacket with a Border emblem patch on his left sleeve, just like his unit.

Personality
Tachikawa is an arrogant character. He also likes to tease Miwa. Kei also acts like Jin, the way of his thinking is more like Jin which makes him unliked by Miwa. Despite that, he's a quite friendly outside the battlefield. He likes to joke around, just like Jin. He is a Unit leader so he is probably a very good tactician.

Yūichi Jin
Kei and Yūichi have a similiar way of thinking. They understand each other. Tachikawa thinks of Jin as a rival and looks forward to fighting with him to see who is the best attacker in Border. When he is not fighting he is quite friendly towards Jin.

Black Trigger Retrieval Arc
Kei returned to the Mikado City from the mission as a part of Expedition Force. He then was informed about a Neighbor who has joined Border. Masamune Kido ordered him to retrieve the black trigger from Yūma. Kei became leader of the operation group and decided to attack as soon as possible to stop Yūma from learning how to use his trigger.

On way to Tamakoma he and his group are confronted by Jin, who wanted to protect his "junior". Arashiyama Unit appeared and teamed up with Jin. Kei and his group kept Jin in check until he used Fūjin. Ultimately Kei and his group lost and they returned to the HQ. Later Tachikawa and Kazama met Jin and talked with him about his decision to give away Fūjin. Tachikawa was really happy that they would fight again for Number 1 Attacker position.

Third Trion Soldier Invasion Arc
Tachikawa was first seen being summoned by Shinoda to fight against the Trion Soldiers. While the Ilgars were attacking the Border base, Tachikawa sprung into the air and slashed one down with his Kogetsu.

History
Kei's mentor was Masafumi Shinoda, the strongest user of white trigger in Border. Jin used to be Tachikawa's rival. He was not able to activate the Black Trigger that Jin has now, so he didn't participate in the competition; which was held between 20 agents, Jin was among them, to get the Black Trigger. Of course, Jin blew them off.

Before Jin had obtained the Black Trigger, Tachikawa was stronger than him, but now it's different. Both of them have to settle things up now.