His first day in Azkaban is miserable.
Because he's innocent, innocent, innocent, and why won't anyone believe him?
(He gets two daily meals - soup and porridge, slipped beneath the door - but that's prisoner food, and he shouldn't be a prisoner.)
And he's howling, because it hurts, being so alone, and knowing that one best friend is dead and one is a traitor and one believes he's betrayed them all.
(That's the one that hurts the most, actually. Because if nothing else, Sirius Black is loyal, and the fact that Remus doesn't realize that means he never knew Sirius at all.)
[100 prompts: Howling]
[Becoming a Wizard: Chore 2 - food]