～いち (にほんいち)
～いち (にほんいち) · ～ichi (nihonichi) · JLPT N2 · noun
no
🥇 日本一 = Japan + one: number one in all of Japan
一 (ichi) means one. Put it after a place or group and it means the best there: 日本一 (nihon-ichi) is the best in Japan, 世界一 (sekai-ichi) is the best in the world.