"does the Note have to be in a human's possession for him to physically interact with our world?"
There are a few other exceptions but that's largely correct, yes. Shinigami can only interact with the human world on specific occasions. Ryuk couldn't just visit to eat apples.
I. When the Shinigami's Death Note is handed to a human. II. Finding a human to take possession of a Death Note should be done from the Shinigami realm, but if it is within 82 hours this may also be done in the human world. III. When a Shinigami stalks an individual with an intention to kill them, as long as it is within 82 hours of possessing them the Shinigami may stay in the human world.
no subject
There are a few other exceptions but that's largely correct, yes. Shinigami can only interact with the human world on specific occasions. Ryuk couldn't just visit to eat apples.
I. When the Shinigami's Death Note is handed to a human.
II. Finding a human to take possession of a Death Note should be done from the Shinigami realm, but if it is within 82 hours this may also be done in the human world.
III. When a Shinigami stalks an individual with an intention to kill them, as long as it is within 82 hours of possessing them the Shinigami may stay in the human world.
https://deathnote.fandom.com/wiki/Rules_of_the_Death_Note/How_to_Read_Rules#IV_The_Shinigami_Rules