Wim has dark hair which he keeps cut in a crew cut. His civilian clothes consist of a long-sleeved shirt and long pants.
Like the rest of the Yeagerists, Wim seems to be a man possessing extreme radical tendencies. Wim feels no qualms about leaking military information to the public or defecting from the military altogether. He also appears to be a fairly trusted member of the group, as he is frequently seen accompanying and personally assisting their de facto leader Floch Forster.
Following Eren Yeager's arrest for disobeying orders, Wim is among the soldiers who leak the news of Eren's detainment to the press to pressure the military into releasing him. After they are caught, the perpetrators are all arrested and Hange Zoë says they will be prosecuted.
The rebels are freed from their cells by guards who have also sided with Eren and rendezvous with Eren himself outside of the city. Eren declares that their next objective will be to find and team up with Zeke.
The group receives word from a Marleyan that Hange has arrived at the restaurant he is working at and storm the restaurant to capture her and the other Survey Corps officers that are with her. When Hange refuses to tell them where Zeke is, they take all of the officers captive and depart for Shiganshina District.
Wim is among the Yeagerists that Floch brings to guard the Azumabito family at Paradis' harbor. When Floch attempts to get Kiyomi to cooperate by executing the Azumabito mechanics, Wim is one of the soldiers that dispose of the bodies.