Tsukishima has an older brother named Akiteru, who was a member of Karasuno's volleyball club at the same time as the Small Giant. Akiteru is both the reason for Tsukishima's interest in volleyball and his current attitude towards it, namely the idea that one should not put too much effort into his club activities because he will only end up getting hurt in the end. Tsukishima used to adore his brother and would often ask him to teach him volleyball skills as soon as Akiteru got home. However, their relationship was destroyed when Akiteru lied to Tsukishima about him being an ace on his team only for Tsukishima to find him in the bleachers during a match. Since then, Tsukishima would avoid talking to Akiteru and whenever the latter came home from college, Tsukishima would lock himself in his room until dinnertime.
After the summer camp in Tokyo, the brothers finally talked to each other about their past and reconciled based on it. They are now slowly putting their relationship back together.
Tsukishima is shown to be close friends with Yamaguchi, who calls him by his nickname Tsukki. When they were younger, Tsukishima rescued Yamaguchi from bullies by calling them pathetic. Because of this, Yamaguchi later became attached to Tsukishima, yearning to be as cool as him.
Yamaguchi and Tsukishima are rarely seen apart. They are both often portrayed making fun of the others together. However, as time went on, their relationship began to drift apart in terms of training. While Yamaguchi persevered in working on his jump float serve, Tsukishima did not exert more effort than needed. This worried Yamaguchi and some of the other members, but they didn't say anything at first. Later on in the summer training camp arc, Tsukishima still refused to put any effort into his training because he did not see why he should. His behavior angered Yamaguchi who for the first time yelled at Tsukishima, asking him what more motivation he needed than pride. This changed Tsukishima's way of thinking and impressed him; he even called Yamaguchi "cool" for the first time. Tsukishima started working harder, and their relationship returned to normal after this event.
Tsukishima initially had a rather antagonistic treatment towards Hinata. He has voiced his dislike of the latter's hot-blooded nature towards volleyball despite his lack in height—even going through the lengths of trying to crush Hinata's spirits during their 3-on-3 match at the start of the series. This is later revealed to have been because of his brother's volleyball history in Karasuno.
Tsukishima also has originally considered himself somehow inferior to Hinata's skills, as noted by some of their teammates and Kuroo. After finding his own love for the sport, Tsukishima has started to have a bit more of a competitive rivalry with Hinata, as the two are both middle blockers.
Tsukishima and Kageyama don't get along at all, mainly because they got off on the wrong foot in the beginning. Tsukishima uses Kageyama's past as a terrible teammate to insult the latter often, and Kageyama would often yell back; their fight almost led to violence at one point. Tsukishima was shocked by Kageyama's change at first, especially when Kageyama asked him about the type of toss he preferred. Since then, the two now view each other as teammates and would work together during matches.
As far as his relationships with his teammates go, they vary though he holds a few members with disdain. For starters, he looked down on both Kageyama and Hinata, the former for his infamous reputation as the bossy king of the court (even calling him by that moniker just to mock him) and the latter for both his short stature and hot-blooded demeanor. This disdain also applies to his second-year senpais Tanaka and Nishinoya, who are also hot-blooded (a trait he found irritating). However, he did hold respect for his third-year senpais Daichi, Sugawara, and Asahi but probably on the account that they are more level-headed. However, before being reprimanded by Yamaguchi for not trying his best, he felt that the team's efforts to improve were futile and thought that in the end, they'll still lose anyways. Unlike the majority of his teammates, Tsukishima is not really attracted to Kiyoko nor did he interact much with her so far.
|Tetsurō Kuroo and Kōtarō Bokuto||
During the summer training camp arc, Tsukishima trained with Kuroo and Bokuto at the request of the latter. In their training matches, Tsukishima received advice from both of them while also paying deep attention to their moves. The two are mainly responsible for Tsukishima's improvement; Kuroo taught Tsukishima the proper way to block successfully and Bokuto taught Tsukishima "that moment", which Tsukishima used as motivation in the Shiratorizawa vs Karasuno match. After the training camp ended, Bokuto and Kuroo start calling Tsukishima by his nickname 'Tsukki', much to the first year's annoyance.