From Bulbapedia, the community-driven Pokémon encyclopedia.
Pokémon with You is a campaign run by the The Pokémon Company to help fundraising and support of the 2011 Tohoku earthquake and tsunami disaster relief. It is partnered with Game Freak, Nintendo, and various other corporations.
After the Tohoku earthquake took place on March 11th, 2011, Pokémon declared that they were going to help. While nobody from Pokémon (or Nintendo for that matter) was directly affected, the repercussions of the disaster spread throughout the nation. Pokémon immediately responded by delaying the opening of the international Pokémon Global Link websites, and in May that they would also assist through the Pokémon with You campaign.
Pokémon with You has hosted several events to both fundraise and boost the morale of the citizens of Tohoku, and usually include an appearance by a person dressed in a Pikachu costume. Fundraising events have included Pokémon hosting tourism festivals as well as sponsored walks. Pokémon with You has also attempted to lift the spirits of the citizens of Tohoku through Pikachu visiting several local schools.
In addition to fundraising through events, Pokémon with You also has a place on their website where those interested can donate to helping the victims of the disasters.
Pokémon Centers have sold various merchandise and given part of their profits to support Pokémon with You. The most notable merchandise was a series of buttons sold by Red Cross for $25 dollars from June 4th through August 31st. Around 50,000 buttons were sold.
Pokémon Center Tohoku
Additionally, Pokémon opened a new Pokémon Center in the area affected by the disaster. On its grand opening, the line to enter the building was so long that people had to wait over five hours to enter.