|“||The world is crueler than children imagine.||”|
Masamune Kido (城戸 正宗 Kido Masamune?) is a character in the manga and anime series World Trigger. The top commanding officer of Border, his actions made him the main antagonist of the Black Trigger Capture Arc.
Masamune Kido has narrowed cheekbones and short, ebony hair slicked back from a slight widow's peak, accompanied by slate grey eyes. He has a scar of unknown origin running down the left side of his lightly tanned face. Kido always maintains a serious, somewhat cold expression. Being a high-ranking member of Border, he usually wears a suit.
In the early days of Border he had longer hair, the fringe was slicked back, framing each side of his face. He also had no scar, which could mean he received the wound during the tragedy before Border went public. In the portrait he left in his old room from the old HQ which is now the Tamakoma Branch base, he wore a navy blue cardigan over a dress shirt along with dress pants and dark loafers. He was also seen grinning.
Kido is a serious and strict person, showing stern condemnation for those breaking Border's rules, such as Osamu Mikumo, but was shown to be somewhat forgiving in retrospect, encouraging Osamu down the line. Kido is also capable of taking extreme actions to accomplish his goals. On the flip side, he can mindfully barter with a discerning eye for keeping procedures prompt and fair. At the sudden request by an agent for a cash incentive from participating in the Expedition Selection Exams, Kido expressed empathy, showing no irritability while promising a generous stipend for those who would pass the tests, despite the former's brashness.
Like most of his faction, he has been shown to hate Neighbors and unilaterally considers them enemies of humanity. This irrational hatred is said to stem from the numerous comrades that died fighting them, but Kido's philosophy towards them appears to be more complex than he lets on; he deemed Yūma Kuga a Neighbor and dangerous entity in spite of his relationship with Yūgo Kuga, Kido's former colleague, but is still permissive of the Neighbors in Tamakoma Branch, including Michael Cronin and the Aristeran refugees. According to Yuri Rindō, Kido's hardline stance against the Neighbors is what attracted many new recruits to Border, implying the motivation behind his populist ideology was increasing the strength of the organization.
Yūichi Jin has suspected that Kido's actions in the Black Trigger Capture Arc run in contrary to his "true goal," the reasoning of which was sufficient to make Kido revoke all threats on Yūma and his Black Trigger; although Director Rindō has stated that he would still seize any opportunity to confiscate it. Nevertheless, during the Border Enlistment Arc, he unwaveringly agreed to honor Yūma's safety so long as he complies with Border regulations, showing more flexibility in his views than he was suggested to have — although Yūma's heritage may have played a role. This leniency was also shown when he agreed to Hyuse's enrollment as an agent.
Kido and Yūma's relationship started off on a bad foot, as Kido saw Yūma as both a hostile Neighbor and a deadly Black Trigger wielder. Despite Yūma being the son of Yūgo Kuga, Kido ordered Yūichi Jin to eliminate Yūma, as there was no proof of the latter's heritage. Kido became more determined to get the Black Trigger and ordered several A-rank squads to go after Yūma, although it should be noted that he didn't mandate the use of lethal force, unlike his earlier order to Jin.
After the top teams were routed by Jin and Kido had to accept Yūma as a Border agent, the commander was more accepting of him, promising Yūma's safety if he followed Border's regulations. He even allowed Yūma to use his Black Trigger during the Second Large-Scale Invasion under the condition that he wouldn't leave the Danger Zone.
- (About Osamu Mikumo) "People who don't abide by Border's rules are not needed in my organization." 
- (About Masafumi Shinoda) "That mischievous brat..." 
- (To Osamu Mikumo) "Work hard to reach your goals." 
- (Following Hiura's resignation) "I wish these young people... All the best in the future..." 
- He likes his family, old movies, and black coffee.
- Expert medical staff attempted to salvage the lost eyebrow from his scar, but failed.