September 2016 Bold indicates part of a mandatory change
Immediate Changes
Nightly transformations and transformation fatigue. This is already causing him to become more nocturnal, as he's having a very hard time sleeping at night and getting up in the morning.
Coarse, thick, black fur on arms, shoulders, upper back and collar bone. Resembles the black pattern pandas have around their front legs. At this point it feels more like a young panda's fur than a full grown one's (so it's a little softer than it will be later). ...As an additional note, all of his fur actually starts out white. That includes what's already grown; he was just too distracted at the time to notice the fur until it was already black (because let me tell you, after everything he heard about changes, painless fur growth was not exactly what he was expecting).
Sharp upper canines. They're a little hard to notice, especially since they have yet to elongate fully, but they definitely look like fangs. Right now they are only present when transformed.
Sharpened Senses. Currently, he only has them in his transformed state. His day form still has a human's eyesight, sense of smell, hearing, etc. This is ALSO not helping with the nocturnal thing because the heightened senses combined with an old ass house and five other people in the same room make it even harder to sleep at night, versus the day where he finds it easier. (Eventually, once he has them during the day he'll be used to it. RIP in peace your sleep schedule though, Choromatsu.)
Weakness to silver. He hasn't discovered this for himself yet though (and he's not about to risk a test to find out).
Gradual Changes
Larger size when transformed. He grows a little more each night; by the end of the month it will be a noticeable height difference (about a foot or so). He will be his full, final size by the end of his mandatory changes.
More fur. With each transformation he has more than he did the night before, starting with the rest of his back. Most of what's growing right now is staying white.
Elongated upper fangs. They grow a little more each night.
Increased strength when transformed. He doesn't have much control over it yet and it just keeps getting stronger, so expect a bunch of stupid shenanigans.
Territorial instincts. His "territory" is the Matsuno house, obviously. Right now he's just a little suspect of people who come into the house and aren't a Matsuno but given so far that's only been Ingway and Ingway tried to EAT HIM it's not really all that out of the ordinary.
Psychological Change: "Mother bear" like protectiveness. This one's very, very gradual. It's over his family, obviously, because I may as well take this "mombro" joke with me to the grave. It's not a whole lot of anything right now but in the future it'll be a lot more primal and uh. Yeah let's hope no one ever tries to attack another Matsuno in front of him because it won't be pretty.
Notes
For now his day form remains mostly the same as when he was a human.
He can still pass for human at night so long as he covers up adequately. This will not last long, but he will take advantage of it for as long as he can.
First Changes
Bold indicates part of a mandatory change
Immediate Changes
...As an additional note, all of his fur actually starts out white. That includes what's already grown; he was just too distracted at the time to notice the fur until it was already black (because let me tell you, after everything he heard about changes, painless fur growth was not exactly what he was expecting).
Gradual Changes
Notes