Be my husband from now on!

Masaki, who lives in a small rural village, has been alone since his grandmother passed away and holding calligraphy lessons for children is his only diversion now.
But recently, a boy who started going to these lessons started proposing,
"I'm your husband now!"
Masaki didn't take him seriously, but one day, after smelling Masaki's scent, out from Sakutarou's head popped...animal ears!? Is that a tail?! Until...POOF!
A young man who resembled Sakutarou, but was taller than Masaki suddenly appears...?!?!
He's sniffed, he's licked, and somehow, he seems kind of dangerous?