Let's be up front about one thing from "go": this is a very lighthearted, extremely campy manga. If it has piqued your interest in any capacity, you need to know this going in. It follows Superman becoming absolutely smitten with different Japanese dishes during his lunch breaks at the Daily Planet and waxing poetic about his experiences with each one, often cracking the kind of hammy jokes and lingo you might expect from a kids' adventure cartoon with the character. Like I said, it's very, very campy and doesn't make itself out to be anything but. Sure, there are a few more serious moments, such as brief panels of fighting bad guys, rescuing people from danger, or a very, very brief glimpse of Supes struggling with Lois Lane not knowing his secret yet and how that impacts his desire to share his passion for Japanese cuisine with her. But these moments aside, the manga doesn't set itself up for having any major plot (at least not in this volume) and it doesn't aim to be anything other than pure, silly fun.
For what my review is worth, I had an inkling of this manga's nature going in, and I was able to enjoy it as an ode to camp and a lighthearted answer to the question it posed of "what would happen if Superman got Japanese food on his lunch breaks?" The art style is playful and lends itself well to the manga's intended nature, and while some of the hammy dialogue made me groan here and there, this is just very much also in the spirit of playful 60s superhero camp. I found it an enjoyable little departure from the norm and I'm very curious to see how many more volumes there are (I know there's already a page for volume 2) and what all is going to happen.