I'm writing this review after reading most of Nekojiru's work, however Cat Soup was my introduction to her. Knowing more about her story, her death, and her work, this short feels like a true love-letter to Nekojiru as a person, rather than just as a creator. It features the more introspective and absurdist chapters from Nekojiru Udon, and strings them together into a beautiful narrative about life and death, and everything between.
This is the kind of thing that requires some background to fully appreciate and understand, however it can still be enjoyed by a complete outsider to Nekojiru's work, although its meanings and message may seem a little vague. I'd highly recommend you watch this, loock at Nekojiru's work, specifically Nekojiru Udon Volume 1, and then go back to watch it a second time.
The art direction is on point, encapsulating Nekojiru's artstyle yet transporting it to another dimension, devoid of most of the blatant shock humor, yet it still makes subtle references to Nekojiru's iconic humor. Nyatto and Nyata's relationship feels very real and human, despite them being neither real nor human.
Cat Soup feels like a journey through Nekojiru's mind; it shows her fears, experiences, and life, through metaphors that play on ideas she initially made in much more light-hearted contexts. It slowly devolves into madness yet showcases the strength of hope and love, a theme that is only vaguely implied in her comics, through Nyatto and Nyata's relationship as siblings.
Overall, this is a perfect capsule of the soul of Nekojiru—all of her dreams, stories, and experiences— and it leaves you feeling melancholic yet appreciative of life and its beauties.