Hiiragi Aoi manga
Also known as "Whispers of the Heart." This heart warming manga was made into a world renowned anime by the famous Hayao MIYAZAKI / 宮崎駿 and Studio Ghibli / スタジオジブリ. Shizuku Tsukishima loves books. One day, she notices that the name Seiji Amasawa appears on the checkout cards of nearly every book she's borrowed! Before she realizes it, her heart is pounding for a boy she's never met...and that's when a mysterious black cat and Shizuku's sense of wonder guide her to an unusual shop--and introduce her to someone she's been curious to meet! Amazing things can happen...when you listen to your heart.
From Viz: When awkward schoolgirl Haru rescues a cat on her way home from school one day, the last thing she expects in return is to be honored by a feline royal family! Before she knows what's happening to her, Haru is drawn into a world inhabited entirely by talking cats--and recruited to be the next Cat Princess! Only the dapper cat Baron and his friends, a magical crow and a comical fat cat, along with a friend from Haru's past, can help her return home.