Episode 15. N finally manages to confess his ties with Team Plasma , which he'd been angsting about ever since the end of Episode 11. Black doesn't mind much. And it's not in the ferris wheel, but on their hotel room bed.
More from episode 15, doubleing as a CMOF. N and Black finally ride the ferris wheel together, and Black finally says N's name with a smile...before N smacks him in the face.
In episode 22, when Cheren calls Black his best friend. Black is taken aback, since they never say it out loud, but happily replies that Cheren is his best friend, too.
The Two Year Anniversary comic (which one could consider canon) where Black kisses N's forehead in an attempt to cheer him up after the events of Episode 24, explaining that his mom would do the same when he was having a bad day.
Alder and Cheren's talk in Episode 27, in which Alder finally shows his serious side and they have a real conversation.