What is the Japanese name for Chinese-style cuisine that includes gyōza?

The Japanese name for Chinese-style cuisine that includes gyōza is chūka ryōri.

Chūka ryōri means Japanese Chinese cuisine: Chinese-inspired food adapted to Japanese ingredients, tastes, and restaurant culture. The shorter term chūka is also widely used. Gyōza, ramen, chūkaman, and many Japanese-style Chinese restaurant dishes are commonly placed within this culinary tradition.

Modern chūka ryōri developed mainly from the late 19th century onward, although Chinese culinary influence in Japan is much older. Chinese immigrants and Japanese people returning from China both helped introduce and reshape dishes. Many popular versions in Japan differ substantially from regional Chinese originals, so chūka should not automatically be treated as the same thing as “authentic Chinese cuisine.”

Washoku refers to traditional Japanese cuisine, while yōshoku generally means Western-influenced Japanese food. Kaiseki is an elaborate Japanese dining tradition. Those terms are therefore related to Japanese food culture but are not the canonical answer to this question.