What is this thing next to the sign on the pedal of Yamaha Fuxi? The pipe is leaking.

It is a valve of secondary air intake/secondary air supply system, and its function is to protect the environment. If the thick hose leaks oil, it will produce a lot of noise, and some may affect the stability of engine operation. Just replace the hose or cut off a section (if there is water leakage near the pipe head) before plugging it in.