T.K. begins to see Tai as an older brother figure in the same way he sees Matt but is unaware of the implications that Matt draws out of this. He also sees Tai as a leader to the group.
As T.K's older brother, Matt always goes out of his way to protect T.K. during their first adventure. At times, however, T.K. would lash out at this whenever he felt that Matt's measures to protect him were too much. When T.K was kidnapped by Puppetmon, Matt almost goes insane and yells at Sora and Biyomon for deleting Kiwimon, Puppetmon's subordinate who knew where he took him. In spite of his frequent frustration at Matt's protectiveness, T.K. still loves his brother dearly, and was even shown to be crestfallen when Matt briefly disappeared from the group and then later chose to briefly leave.
During the second adventure, T.K. starts to feel the impact of his parents' divorce and decides that he should see Matt more often.
Sora is like T.K.'s older sister figure, and T.K. goes to her for anything more mature. T.K. Also told her that when ever she's around he doesn't miss his mother as much.
T.K and Izzy have had their share of childlike interactions, such as when they experimented on whether Izzy's computer codes could digivolve Patamon and when they slept-talk to one another during their train ride to Odaiba.
T.K. is interested in why Mimi has her strange quirks but still sees her as a good friend and companion.
According to Joe, he was in his wood working class in summer camp, and T.K. nearly cut off one of his fingers. Joe has risked his own life to save him on at least two occasions.
T.K. visibly spends a lot of time with Kari during both seasons, although it is clear both have fallen out of touch with each other during the intervening years. They seem to relate to each other the best throughout both series, both having a great deal of experience with Digimon.
In Digimon Adventure tri., the pair continues to have a close relationship. T.K. intends to bring a friend to his brother's live performance; Kari susses out that it's a girl and teases him about having a girlfriend. T.K. denies that she's his girlfriend and jokes about Kari being jealous, which she dismisses in the same manner. When teased by Matt about the same subject, however, he dodges the inference but does not outright deny it.
|This information is only considered valid within the English continuity.|
In the engish dub version, he admits that he cares about her a great deal and fears losing her during her struggles with the Dark Ocean. [please confirm]
|This information is only considered valid within the Chinese continuity.|
Sora implies they kissed under a mistletoe on Christmas.
In Takeru's character song, "Focus", he describes someone who seems similar to Kari, and in the chorus, he asks, "Am I the focus of your heart?"
Despite Davis's beliefs, T.K. does not try to compete with him for control of the group, and is generally content to be merely amused with his antics despite sometimes disagreeing with him. However, T.K. will take over when Davis is absent, and much like Matt does for Tai, he tries to talk sense into Davis when Davis is acting irrationally. Despite Davis's frequent insecure rudeness to T.K., T.K. is usually more sympathetic to his actions than Matt and Tai are.
T.K. is aware of Davis's unrequited feelings for Kari, and enjoys occasionally teasing Davis by making him jealous of their preexisting relationship.
T.K. lives in the same apartment building where Yolei lives. Also, in Episode 1, he is seen using the same lift as Yolei and in Episode 2, he reveals to his fellow friends that one of the new DigiDestined is a girl living at the same apartment as him.
Cody and T.K. are very close henceforth how their two Digimon fuse together and Cody is sometimes shown to be really worried about him, such as the time Cody asked Matt about why he was nervous to let Patamon battle.
T.K. at first is cold and bitter towards Ken and is disgusted at his ideas of "toying" with darkness; he manages to take Ken down in a stream of insults and logic, and manages to shock him so that he can fight Ken momentarily (even though Ken is a master at judo at that point).
T.K. is still, however, forgiving, and he is the first one after Davis to accept Ken into the group (in the Japanese version, he agreed with Davis that Ken had changed, but still was against him joining until Ken apologized to the DigiDestined), and comes to care for him a great deal.