What is Time Character getting ice cream??

Ice cream quest, for the lottery.

Your observation of the event details is quite sharp. While I'm still confirming the specific use of this item, usually these kinds of items are used on the event page after accumulating a certain amount. I recommend checking the in-game event description first, as you might find clearer instructions there.

Thanks everyone for the replies, got it~

Like a lottery ticket.

For the lottery.

You can use it for a lottery.

It's fun, but you'll need to get the item levels super high later on.