When Takato and Henry first met, it was at school where Terriermon tactlessly insulted Takato. Takato, rather than take offense was saddened and realized that he needed to exercise more control over Guilmon. Henry later becomes Takato's mentor in using cards as Henry had been a tamer far longer than Takato. They evolved a close bond after being stranded together in the Digital World.
At first, Henry dislikes Rika because of her belief that Digimon are just weapons and can only fight. This belief slowly changes as Rika begins to realize that Digimon are not weapons. They are close friends but their only bonds seem to be Takato and their digimon.
Henry and Kazu do not interact much.
Suzie is Henry's sister. She starts out as a very minor character, appearing only to play with Terriermon, to play with him thinking he's a doll and continuing to do this when she is a tamer with Terriermon and Lopmon. When Henry travels to the Digital World, rather than leave Suzie wondering where he went, he tells her the truth and even lets her know that Terriermon is alive. When Suzie becomes a Tamer however, Henry becomes very over-protective of her, forbidding her to be with Lopmon to confront the Sovereign, and forcing her to stay with Kazu and Kenta. He even goes so far is to yell at her to stay. Henry also states that he wants to find Calumon so he can send his sister back, because it is too dangerous for her.