Quote Originally Posted by Unregistered View Post
I haven't done it, but from what I understand-
first, the girl has to request the memento, through the level up requirements. Apparently, they don't drop from the gacha unless they are needed
second, click on the girl who needs the item, and wake her up (not sleeping, not doing a task)
third, use some of your (hoarded) promotional tickets from the dailies, and hope.

of course, the premium gacha have a better chance, but those cost gems. From other comments, the first requirement is the important one- if a girl is not requesting a memento, it will not drop from the gacha. This has NOT been confirmed on the discord server- perhaps you can ask a developer there.
Thank you so much.