Bleach Movie 1: Memories of Nobody is a movie that you can watch immediately after the Soul Society arc in the Bleach manga and right after the Bount arc in the Bleach anime, being the first exposer to Rukia Kuchiki's Zanpakuto. It is the only Bleach movie that can fit into the main continuity without much trouble.
The story is about the worlds about to be destroyed by the enemies called the DARK ONES. Some of the blandest antagonists you will see in Bleach and can be a total turn off for people that are interested in a well written antagonist with a deep backstory. However, they do have justification for what they do even if not the smallest effort was put for use to care about them.

On the contrary we have Senna and the story is focusing on who she really is as she has Shinigami powers and a named Zanpakuto. That is the only remotely interesting part of the movie and there is no surprise that non of the DARK ONES made it into video games but Senna did.

Ichigo Kurosaki in this movie takes the role as her guard protecting her from the DARK ONES and Soul Society because that is Ichigo for you. In the movies he is always the character who does and says the right thing while the other characters are just following orders or their selfish desires.
Senna is a playful self-centered girl but cares about finding the truth about herself. Not because she has amnesia, thank god. The movie takes a lot of time exploring her personality, her desires and fears. It will make you believe she needs to be protected.

As for other characters, Urahara does the usual helping out thing. The other main cast members are usually shafted with Orihime only healing once after the battle. Like most Bleach movies it focuses on the Shinigami doing the fighting. And let me tell you there are a bunch of Shinigami eating up screentime with their Zanpakuto releases and BANKAI.
Speaking of fights, they were rather mediocre. Soifon got the best treatment of all Bleach movies in this one by not making her look like an amateur. Some enemies used their energy sources they intend to destroy the worlds with in a clever way in some fight, for example the guy who fights Toshiro Hitsugaya. But that is as far as the compliment goes simply because like in all Bleach movies the Captains just slaughter the opposition with almost no effort.
Some of the enemies weapons are also uber lame and aren't used in an interesting way to make up for the lack of interesting powers.

Overall this movie is the weakest Bleach movie. Senna is the only thing that is interesting but the antagonist don't feel as dangerous as they should since the high tier shinigami are around. If you want to see where the truth about Senna lies, you may enjoy this story and the ending will be hitting you hard emotionally. If you looking for an action packed Bleach movie with interesting antagonists and killer visuals you might want to skip that. Especially if you aren't a fan of Bleach filler since this movie feels like an extended filler episode than a movie.