This last event was pretty rough for me, day 7 got my first girl and on the last day I bought 2 extra rounds of attacks to get the other one.

Also in my opinion it's almost always worth buying attacks (on the last day) for girls from the fights because it will, most likely, be way cheaper then pachinko. During the anniversary I spent something like 1k kobans and ended up getting 7 girls and a ton of money since it was the last mission.