Who killed Natsumi?

Could you please elaborate on the mysterious circumstances surrounding the death of Natsumi? Who is the prime suspect in this case, and what evidence has been gathered so far? Have there been any witnesses who have come forward with information? Additionally, are there any unusual details about the crime scene or the victim's personal life that could provide clues to the identity of the perpetrator? It's crucial that we uncover the truth behind this tragic event and bring justice to Natsumi's family.