After debugging and memory searching, I got the Key and IVYes. If PC save files get cracked, I'll add a converter between PS4/Switch and PC saves.
For PC gamesave:
rijndael.Key = new byte[] { 0x46, 0x5C, 0x42, 0x2B, 0x65, 0x50, 0x34, 0x3A, 0x38, 0x32, 0x28, 0x70, 0x4D, 0x76, 0x2B, 0x49 };
rijndael.IV = new byte[] { 0xF3, 0xF4, 0x5F, 0x18, 0xD6, 0xC2, 0xB6, 0xE6, 0xFA, 0xEE, 0x88, 0xAE, 0x57, 0xE5, 0x8E, 0x1A };
rijndael.KeySize = 128;
rijndael.BlockSize = 128;
rijndael.Padding = PaddingMode.None;
Also stearming assets file key/IV was found
rijndael.Key = Encoding.UTF8.GetBytes("mk:9tzxWRF}Jpzw2");
rijndael.IV = Encoding.UTF8.GetBytes("NFXjeq(n:3g'8&=;");
Good luck Taishiro !