"Grandpa". There's nothing Tsuna doesn't trust him with. No longer quite the perfect "hero" Tsuna imagined, but someone who is irreplaceably dear to him and close to his heart regardless. He's the only person Tsuna's actually comfortable having physical contact with, such as hugging or getting his hair rustled.
"Home tutor". The person of whom Tsuna simultaneously cares for a lot and is terrified by. In Paradisa, their relationship remains much the same, and trying circumstances have only brought them closer together. After a mishap while passing into the Dead Zone during an expedition, Tsuna is now familiar with his adult form along with his cursed form.
"Big sis". He trusts her more than anyone else in the castle, and is the only person he's willing to talk to about mafia-related issues. He's eternally grateful for all she's done for him, and really, saying he depends on her isn't an exaggeration. Ino makes Paradisa his home away from home.
Also something like Tsuna's big brother figure. He has a lot of respect for Allen and even admires him to some extent. ... probably the only remotely healthy idol he has. They get along well and bond through hardships, shonenness and video games.
A girl who was his cousin during the family reunion. Ever since, they've kept in touch and have been good friends. They've helped support each other through their nightmares, and enjoy hanging out together.
Kind, calm, and caring. He's seen her death, and learned about how her brother created the mana lineage. He trusts her, and finds her presence very soothing. Also has... s..omething with Reborn?? But she's engaged to someone who left the castle? what is their relationship even.
A militant-like Arcobaleno whose spartan ways rival Reborn's. Tsuna knows he's a good guy and a great fighter, but quite frankly, he's terrified of him. Like Reborn, Tsuna is aware of his adult form.
Properly introduced during a nightmare. Which was not fun, by the way. Somehow ended up talking to him more anyway. Really friendly guy! ... too friendly sometimes. Still, Tsuna likes him a lot.
Guy who likes to drag him around to do adventurous things and is occasionally a troublemaker. Kind of a pain sometimes, but Tsuna likes him all the same when he's not trying to get the boy killed on flying brooms.