I like that the devs are trying something new, but in the future I think this event could use a slight improvement. Here's my reasoning:
I can get an Epic Pachinko girl 100% of the time for 5400 kobans. If a limited-time event also has an Epic Pachinko girl on a villain, I expect to win her for less than 5400 kobans. (If not, I'm better off not participating in the event and playing epic pachinko instead.)
1 combativity point is worth 10.8 kobans. 5400/10.8 = 500 battles. The question is: can I win the girl in under 500 battles?
Given this event's parameters (0shards=90%, 1shard=2.5%, 2shards=2.5%, 3shards=2.5%, 4shards=2.5%), the probability of getting 100 shards in under 500 battles is 91.7%. That's good, but it's not great. One in 12 players participating in the event won't get their girl in 500 battles, and they'll feel cheated.
By contrast, during Epic Days (0shards=90%, 1shard=2%, 2shards=2%, 3shards=2%, 4shards=2%, 5shards=2%), the probability of getting 100 shards in under 500 battles is 99.1%. That's much better.
So my recommendation for future Foreplay events: increase the shard drops from 1-4 to 1-5. Or alternatively, don't include Epic Pachinko girls in it.