The italian part is 100% just clickbait and to make the title more memorable lol.
This is just a SoL self-insert fantasy (illustrator MC?) where an exotic looking girl suddenly appears and has contrived reasons for knowing, living with, and liking the main character.
The italian part could be dropped and absolutely nothing in the story would change, and readers would be less frustrated. The girl would have odd hair and an odd name but for all purposes would be a japanese native going by a nickname, who for some reason is incredibly fond of someone she last met 17 years ago.
As a marketing gimmick its very effective though. Kudos to the author lol