The best example however is the Guild Alliance formed to combat Oracion Seis.

The various teams in the Fairy Tail guild like Shadow Gear and the Raijinshuu are already True Companions and the guild is pretty much a very large set of True Companions bordering on a Band Of Brothers due to sheer size and the often dangerous nature of their jobs.

It's their becoming a proper Band Of Brothers, rather than just a group of people sharing a ship, that makes the ending as poignant and difficult as it is.

The main cast of Cowboy Bebop becomes this, but only very late in the series.

The Black Knights in Code Geass is La Résistance under the The Chess Master Lelouch.

(They're based on the Three Musketeers.)''. The three Gun-swordsmen in Brigadoon: Marin and Melan are supposed to function like this, though differences of opinion get in the way.Though three of their companions (Bertolt, Reiner, and Annie) happened to be the enemy while Ymir defected to their side to protect Krista, the remaining members became part of Levi's new squad.

Most of them even follow Eren into the Survey Corps against their own wishes. The 104th Trainee Corps in Attack on Titan just after the Battle of Trost.The Wild Hunt however is a notable exception, unlike the other teams they are effectively an outfit of mercenaries run by their leader. In Akame ga Kill!, Night Raid and the Jaegers are this albeit fighting on different sides being the Rebellion's wetwork crew and the Empire's special ops team respectively.

Band of brother