His name is Hiroshi, he's a blackbelt in karate, workin for the city, he's stuffed & toilet paper.

If this note was summed up in one sentence, it would be "welcome to the building, I'm sad and desperate to talk to you." We can't be too mad, since his most eloquent sentence was "I can't speak English." So let's do some detective work. The person who got this had given Hiroshi a present earlier. Check. His name is Hiroshi and he's fifty two. He's either a divorcee who lives alone, or he lives alone with his regrets about his divorce. Check. There's no period on the next line, so it's "You can use it if you like I'm stuffed and toilet paper." Pretty sure that means "You can use my stuff and toilet paper if you like." Like all Japanese people, Hiroshi is concerned his new American neighbor has a navy. Understandable. He wants to know his neighbor's kid's name. Check. He has already paid to have his neighbor's kidney removed to sell on the black market. Check.

Sources: Redditor Theresa52