Soejima's first work for the series was as part of the digital coloring team for the first "Devil Summoner". He later had minor roles in artwork and character design in the first "Persona" and "Soul Hackers". He later did the secondary characters for the "Persona 2" duology, and was also part of the team checking over the PlayStation ports of the first three "Shin Megami Tensei" games, as well as minor work on "Nocturne". Soejima was chosen as the lead designer for "Persona 3" by Kaneko, as Kaneko wanted the younger staff members to gain experience. "Persona 3" proved challenging for Soejima as he needed to refine his drawing style and take the expectations of series fans into account. He would go on to design for "Persona 3/FES" and "Portable", "Persona 4", and "Persona 5". Soejima's drawing style is recognized as being lighter-toned than Kaneko's work on the "Shin Megami Tensei" games.