While you were sleeping...
Four Shadows is a three person unit of assassin/bounty hunters encountered by the group on The Long Runner. Originally comprised of four members, the leader had revealed to Noh that one of their members had recently been killed and corrupted.
Yoshida Kazushige (Leader)
All three sport heavily modified ghost morphs that are enhanced with illegal experimental technology. Also have varying degrees of ultra-human speed, thought processing, and healing. Each specializes in close combat with blade weapons.
Yoshida has spent time testing and training Noh during the two week journey aboard The Long Runner, and has left an open offer to join them/call on them.
Morri had a lot of sex with Monty on the second half of the journey.
Kawaii seems to keep to himself for the most part.