When Raguna first meets him, Gelwein doesn't say anything to him at all. Iris Blanche will then explain that he is very intelligent and tells interesting stories, giving the impression that he's a very nice man. However, when Raguna discovers he's evil, Gelwein is very angry and controlling over Iris Noire. He doesn't seem to care about the suffering of others.
Gelwein used to work for the Imperial Magic Research Center in the Kingdom of Norad, where they were researching for a way to utilize Runes effectively. Gelwein's reputation there wasn't very good, but he was one of the best researchers there. But as time went on, he began to research into using Runes for war, which was forbidden in the Kingdom. As a result, he was fired from the research center. Angered, Gelwein then sought revenge on the monarchy.
He then discovered about the two Irises that kept Whale Island in balance. Shortly after that, he hatched a plan to collect the Runes from Whale Island so he can use them for his revenge. He befriended Iris Blanche and stopped her from singing, whilst using his knowledge to brainwash Iris Noire and force her to sing to collect all the Runes. Raguna soon stops his plan and breaks his hold over Iris Noire, but Gelwein retaliates by kidnapping Mist and using her instead.
- Gelwein will participate in the Pumpkin Festival despite not being a member of Trampoli. If you reach a part of the plot involving him on Summer 30th, he will be wearing a Pumpkin Mask.
- Gelwein and Erik share the same English voice actor.