Atomcat

From the Digital Manga edition

Reading the 'Tetsuwan Atom' (popularized in America as 'Astro Boy') comic book with his dad is Tsugio's one refuge from merciless school bullies. And even then, without a single friend, Tsugio can't catch a break. One day he finds an abandoned kitten, and names it after the robot hero to convince his family to keep it. But after a strange encounter with aliens honeymooning on Earth, Tsugio's shocked to find his cat can speak-- and has all of Astro Boy's powers! Sworn to secrecy, Tsugio and Earth's tiniest hero find themselves entangled with demonic cats, pirate ghosts, a crime syndicate, and more!

Source: OpenLibrary