Pokémon Adventures: Black and White Vol 5

From the VIZ Media edition

White tests out a Pokemon battleground prototype: the Battle Subway. Meanwhile, Black is happily reunited with an old friend... under unhappy circumstances. Then Gym Leader Clay reveals a dangerous secret. Now Black must prove himself to the other Unova Gym Leaders so he can join their team to fight a common enemy - an evil organization that might jeopardize the Pokemon League Championship itself! Will Black earn the trust of the Unova Gym Leaders in time... by ringing a bell?!

Source: Anime News Network Encyclopedia