Those who follow the official Akatsuki no Kiseki twitter account (@akatsuki_ujj) will receive Mueller for free. This event will continue until the day the game goes live.
On top of this, the twitter campaign will upgrade in stages, like with the Noel campaign.
At 3000 followers, everyone will receive Mueller Vander (?1).
At 5000 followers, everyone will receive Mueller Vander (?2).
At 7000 followers, everyone will receive Mueller Vander (?3).
To participate, you will want to register for the account first, then follow the official twitter account.
OpenID accounts through Twitter and Google should also be included. The present item will be given out after the event ends.
As a note, I don’t see anything for individuals that have already followed it, but I assume that there may be something matching related?