I'm not a fan of films that try to look at aspects of an original film from differing perspectives. 
In essence Alienoid: Return to the Future does just that. Its rein-visions and adds to, aspects of the original story. Having watched the first film I still found this follow up horribly confusing. It would have been much better as a clear cut continuance with its own unique but related story.
instead, for this reviewer Alienoid: Return to the Future comes across as fragmentary and as a result difficult to follow. Its not helped by constant shifts between plot elements and characters, with no concise tie in. 
Acting is decent, as per the last film, action is reasonable and special effects are solid. That said, the lack of consideration of a cohesive plot lets this film down, very badly. 
In summary, its hard to recommend a follow up film that's this fragmented and hard to follow. Not recommended.