It’s -extremely- cute, beautiful and very well done. There’s lots of Japanese characters (letters), especially on the box that is taped shut at the end.
Tsubaki got the translation right. As for what mona is, it’s sort of a mascot of a famous - or shall I say, infamous - Japanese on-line message board called Channel 2. I say infamous because it’s an unmoderated anonymous message board with extremely low signal-to-noise ratio. (Tsubaki might find the bicycle section interesting.) One of the common phrases on that board is “omaemona” which means “you too,” usually used to return an insult. This phrase can also mean “you are mona.” Somehow this name “mona” got attributed to an ASCII drawing of a cat-like character which pops up all over that message board. This explains the strange face on that singing cat - it retains the ASCII face. (Actually it’s not pure ASCII, it’s made up of characters from the Japanese character set.)