Hans is a skilled mechanic who is part of Vyse's pirate crew.
One of the many adopted sons of Centime the Tinkerer, Hans takes after his father in a lot of ways - while he still has a lot to learn, he's an expert mechanic with a brilliant mind. He looks up to Vyse both as a friend and captain, and was eager to join the crew of Vyse's ship from the moment they first met in Horteka, even before Vyse had a ship to call his own.
Talk to him after obtaining the Blue Moon Crystal. If he doesn't join right away, leave and come back a second time. He will then join your crew.
If you have Hans active in your crew, he will increase your ship's Magic Defense. His ability is passive and can therefore not be used during ship battles. His skills heal the party in "Blue Rogues attack". He comes out from the smoke and says: "Your rejuvenator is ready to go!"