December
There was a piano in Fuka's room. Kokoro heard someone playing piano in June, probably it was Fuka.
"Sensei" as suffix
The Japanese word "Sensei" means "teacher." It is often used as an honorific suffix for calling a teacher or a doctor.
"Misudo"
"Misudo" is an abbreviation of "Mister Donut."
Kokoro and her friends held a Christmas Party at the castle. They enjoyed.
Rion gave a present to the Wolf Queen. (The gift is not described in detail.)
"One Piece"
"One Piece" is one of the most famous manga in Japan, starting in 1997.
At the end of the Party, Masamune said he would go to school on January 10th. And He asked the other six to go to school on that day so that they could help each other.
Japanese Educational Stytem
Starts in April, the second term starts in September, and the third term starts in January.