Ah, I think that's the chocolate cake.
Bamba stepped on a cake that fell off the table.
When did he step on that?
Before Hatsune left to go to the nail salon.
Ah, so that's it!
At the time of her death, it was raining heavily. So if he'd walked out in that,
then this cream should've been mostly washed off.
Especially if he hurried back here after murdering her!