Cases that full of journeys

Dear friend. I know this is sudden but we need your help. In this few days we keep getting letters that give threat to us. So we really need your help. In this place there are also cases that you and 'the other detectives' can solves it. You can also bring your things, sisters and your friends. See you at Japan -Akehoshi Shora
A letter were send to Reazelf right in front of her house. She know who's the sender. But, that's mean she need to leave Malaysia for a while??!! Who is this Shora Akehoshi? Why she need to solves cases at there? Who is the other detectives that mentioned in that letter?