The internal struggle Shinichi Izumi undertake throughout the series. You really feel for him and his parasytic partner Migi. Without spoiling the end, I will say that the growth of those two characters together is eye watering. I cried tears of both sorrow and joy at the end of this series.
The main problem with this show is a problem that plagues other anime. It's the random harem of girls syndrome. Female characters with no depth or characterization apart from the fact that they are in love with the protagonist. One of the more interesting characters in the series (or so I thought) plot went absolutely nowhere! You waste time seeing this character for many episodes with no real closure leaving this time suck feeling in your head. The main love interest of Shinichi Izumi doesn't really go anywhere either. She loves him more or less the same throughout the entire series with no growth really as a human being. You do see how bothered she is by the struggle that Shinichi goes through and you do grow to care bout her in that respects. But apart from that she has no character of her own. The show would have done better with more emphasis on the dynamic between Shinichi and Migi instead.
Overall: Great series with an intriguing plot and well done protagonist. But otherwise has weak and mindless female characters that dominate the screen. The Music is astounding and leaves you breathless in the most emotionally gripping sections of the show. I do recommend a watch. But to give it any higher than an 8 would be an insult to other anime that properly give attention to all characters.
