Level 15 and Level 17 Surprise Rewards
My advice and instinct is not to stop playing even after receiving all existing rewards. Why can bonding levels continue to increase if there will not be more surprises in the future? And if not, new conversations may be added.
At Level 16, he receives the ability to dress as The Hound!
At Level 17, he will give you the Recipe for The Hound's Cap

As I suspected, Clarice will give you the Recipe for the Veyron Cutout at Level 15.
At Level 15, Cuilang gives a Life-Sized Woolby Cutout Recipe.
It is at Level 15 that surprise Rewards are given.
Subaru will give you your cutout when you play as a girl.
Mauro will give you a Recipe for a Porcoline Decoration.
Fubuki will give you a cutout of the Hound!
I always felt sad that the Hound was not given a place in Azuma after his last defeat.
Hina gives a Life-Sized Nine-Tails.
These Level 15 Rewards, unlike the Level 12 and Level 13 Rewards, are given only by a few characters.
There are Rewards at lower levels as well:
Kotaro at Lv 4 gives a Leaf Hairpin Recipe.
Other Recipe Rewards:
Ikaruga gives Mystic’s Cap
Hina gives SEED Cap
Mauro gives Adventurer’s Cap
Kurama gives Round Glasses
Kanata gives Bunny-Ear Headband
Iroha gives
Clarice gives Commander’s Cap Recipe at Lv 5
Clarice gives Clarice’s Sabre Recipe at Lv 6