Teamwork as a theme
Teamwork is a prominent theme in general in Assassination Classroom concerning E-Class. Being a group that in many ways reflects the wider themes in E-Class in their own unique ways, I feel it is particularly pronounced with the Terasaka Gang.
Alongside the Gang’s themes of growth and belonging, another extraordinarily present factor of their relationship is their teamwork. It’s one of those themes their dynamic can be defined by, and something I believe is critical to understanding their relationship. And this teamwork stems from their trust in one another, from that belonging they feel.
Furthermore is how they use this teamwork as a weapon to assist their classmates — with assassination or otherwise. It is notable how Itona goes from being a solo assassin relying on no one but Shiro (who he has no choice but to rely on) to a key cog in a machine fueled by teamwork.
The earliest instance is in the very first episode, antagonistic a moment it may be for them. However, the first time the Gang’s teamwork ties into their growth as individuals and when it’s used to the benefit of their peers is during the summer exams where Terasaka, Yoshida, Muramatsu and Hazama work together in striving for full marks in their home economics exam, exploiting a loophole in the class’ deal with Korosensei. It’s a feat acknowledged to be extremely tough given the nature of the exam and the subject and so Korosensei acknowledges it must have taken extensive research and, additionally, it can be inferred to have required a deal of trust between them to each achieve 100% because of how they worked towards it together.

The home economics plot is the most major example of their teamwork receiving primary focus, but there are miscellaneous moments such as when E-Class are taking back the mountain, and we are given this panel with this specific text:

Here the Gang who are highlighted for their skills as a team. For as brief a moment as this is (as many moments from the supporting cast of Assassination Classroom are), it reifies the information we’re given in extra material about Terasaka’s leadership skills and the Gang’s ability to work together in every aspect of their lives. For Terasaka, Muramatsu and Hazama it conveys how they have become part of the assassination attempt in opposition to their apathy at the start of the series and for Itona it conveys his transition from a solo assassin to a member of a team.
Their ability to work together is emphasised across the information provided on their relationship in extra material. Karasuma’s report card relays Terasaka & Itona and Yoshida & Muramatsu’s incredible skill with knives when working as a pair (which leads into a note on their their character growth. The official character databook (Roll Book Time) details Yoshida and Itona’s forming of the tech team and their ability to collaborate with each other, combining Itona’s skill with electronics and Yoshida’s skill with vehicle mechanics. Further in Yoshida’s profile we are told of his and Muramatsu’s “harmonisation”, with the kanji used to describe that being an idiomatic expression relating to “dancing to the same beat” and their trust in one another that formulates their kamikaze striker attack.
Teamwork is continuously emphasised as ingrained in their relationship. So much so that, as stated in Yoshida’s character profile, it is something recognised and respected by the rest of the class, and something their classmates have faith in as demonstrated in moments like taking back the mountain and the pole toppling. Understanding this and the importance teamwork holds in shaping their relationship is crucial to understanding the Terasaka Gang overall.