Bleach Movie 2: The DiamondDust Rebellion is a film focusing on at the time Japan's most favorite Bleach character Toshiro Hitsugaya with someone important from his past, Kusaka Sojiro, appearing as the main antagonist.

In concept it is an interesting story since there is an unfinished business between the Captain of Squad 10 and Kusaka which lead to Hitsugaya abandoning his post to solve it which lead to him being labelled as a traitor.

Sadly that doesn't go too well as there is no good reason why Kusaka is as powerful as he is prior to unleashing the power of a plot device Squad 10 suppose to protect and that Kusaka has Arrancar as well as Hollows under his command.
As with almost all Bleach movies, the cast is too large to make a decent 90 minute film and get the most out of it. Meaning Inoue, Sado and Uryu get shafted like in most films in favor for Ichigo and the Shinigami. Meaning you have to prepare yourselves for a bunch of BAN-KAI releases eating runtime. Thus there is not a single memorable scene that stands out as many of the good ones are just inferior versions of the main story ones.

As where this story could fit, it has to be before Ichigo fights Grimmjow the second time with the Shinigami being brought back to Soul Society for whatever reason and Aizen drinking tea or something. It may not really fit to the main continuity, but at least that would be the place where you can be sure when to watch this.

The character arc of Hitsugaya is fine. Not something that impressive but him learning from Ichigo that he doesn't have to carry the burden alone is a good message nonetheless.
Kusaka has a good backstory which will make you hate Central 46 even more but as a villain he seems rather underwhelming. There is justification for what he does but not how easy he archives his goal.
We see a bit of Rangiku's struggle but she isn't that impactful to the film despite being second in command in Squad 10. Not to say she didn't do anything.
Kyoraku, Nanao, Ukitake, Mayuri and Byakuya were also coming in clutch during the investigation and analysis about the identity and truth about Kusaka giving them a role besides just receiving information, reacting and defeating enemies with their Shikai or Bankai.

Fights themselves are really underwhelming with the Captains just showing off like always. And some annoying cliches with Soifon being incompetent so she can be rescued.
However, Ichigo's first encounter with Kusaka had some good use of sharing thoughts through Zanpakuto clashing, a decent use of the abilities of ones weapons and the enemies using teamwork in a visually pleasing way instead of taking turns which is usual for Bleach fights.

Overall this movie was average. The fights weren't memorable. And characters that should get more focus didn't get the care they needed. It is a shame that Kusaka despite his backstory didn't leave much of an impact as a character since the plot device worked however the plot wanted it to be. Like the previous and later Bleach movies, it can't reach its full potential wasting lots of times for fan service. There are too many character and a generic slaughter of weak characters by the high tier Shinigami.
But the finale was still good for Bleach movie standards. If you are a Toshiro fan, give it a go.