By the way, I've been wondering...

How doth the moon cause thine transformation?

To put it simply, the moon sends out different sorts of waves.

Those waves are reset about every 28 days.

That reset happens on the night of the full moon.

During that reset the waves curbing our transformations disappear, and that's when it happens.

Is that the same reason youkai grow stronger under the full moon?

Yes, indeed.

The waves amplifying our powers are at their strongest during the reset.

However, all that only applies while the moon is up.

When it goes down, all the waves' effects become faint.

The sun drowns them out, you see.