Why did Sunny change his name to Omori?

Could you elaborate on the reasons behind Sunny's decision to change his name to Omori? Was it a personal choice, perhaps motivated by a desire for a fresh start or a new identity? Or was there some external factor, such as a legal obligation or a professional necessity, that led to the name change? Understanding the context and motivations behind this change could provide valuable insights into Sunny's character and the circumstances surrounding his decision.