As the synopsis states, Takanashi Rikka Kai is simply a recap of the first season of the TV-series, however it is (naturally) shorted down immensely and also mostly seen from Rikka's perspective this time around. Most of the side stories are cut off, and the movie focuses almost solely on the relationship development between Yuuta and Rikka, which in the end is the most important part of the story, however in the very rushed format that the movie version has it definitely didn't come out as good in comparison in the end. Then again I guess that is somewhat to be expected when it comes to recap movies.
That is not quite all there is to it however (almost though), as you can roughly divide this film into three parts:
The first 10 minutes consist entirely of new content which tries to showcase just how good the "Chuuni-fights" will look when enhanced with modern day cinema-quality CGs (on top of KyoAni's typically high production values), as well as being just the good old Chuunibyou comedy and everything else that comes along with it.
The second part is basically the story itself which covers maybe 75% of the playtime, and it is pretty much simply what I stated earlier. If you've got a crystal clear recollection of the events of the first season of the TV-series you will notice some minor changes every so often regarding the spoken lines, music and shorter scenes but 95% of it is material you've already seen in the original anime airing.
Finally the third part covering roughly the final 10 minutes of the movie is partially an epilogue to the story thus far, and also a bit of a preview/teaser for the second season of the TV-series, which at the time this movie had its subs released had already started airing almost 2 months prior so most likely there won't be anything in the final part that will be news to you either if you're a fan of the series.
As a final verdict then, would I consider Takanashi Rikka Kai worth watching?
If you're a fan of the series, then yes I would recommend you to at least try it out. No, it is not as good as the TV-series, nor is there a whole lot of material that you won't already have seen but hey it's still Chuunibyou, and you can never go wrong with that.
If you're someone who merely thought the TV-series was alright but nothing spectacular, then I would probably recommend you to watch the first 10 minutes of it, as that was the only *really* new segment and since I'm going by the assumption that whomever reads this has already seen at least the first season, then with that taken into account the opening part was quite frankly the best part of the entire movie.
Overall, this is definitely not the best way to properly enjoy the Chuunibyou franchise, but if you're just looking for some additional icing on the cake, you need not look any further than this.
