A mainlander with a sticker that means "accepting a challenge" is overestimating himself/herself. A Beemer?
Meh.

One of his fellow mainlanders that drives an exotic is gonna smoke him a race.
Easy bragging rights. :lawl:

乱入受付中
ran'nyuu uketsuke-chuu

乱入 = Intrusion/raid (i.e. "throwing down the gauntlet")
受付[する] (うけつけ) = "To recieve" or "to accept"
中 (ちゅう) = Suffix that means "currently in the process of doing <verb>"

In other words, it means "I am accepting your challenge [throwdown]". I've seen this phrase used by competitive arcade communities in Japan, like for WMMT5 or Initial D Arcade Stage. If you're playing at a multiplayer arcade machine alone (in 1P mode), and a second player challenges you in multiplayer head-to-head, and you accept, that's basically what the phrase means. Think of "here comes a new challenger" in Street Fighter.

Source: Armchair weeb

^ Thanks for the explanation. I thought it meant "accepting intrusion"...

Okay, that actually sounds pretty dirty.