undulating gable; cusped gable; karahafu
A traditional Japanese architectural feature: a gable with a distinctive bow-shaped curve at the top, often seen on temples, castles, and gates.
The Karamon gate at Nijō Castle has a magnificent undulating gable.
You can see a cusped gable on the roof of the shrine's main hall.
Formed from 唐, here marking an ornate or exotic style, and 破風, “gable.” The architectural form developed in Japan, though its name evokes continental styling.