Still listing the differences between Yumina and Aselia, in Aselia you controled more than one group of 3 people, where one was the attacker, one was the defender and only one was left for skill use- While in Yumina, you have the forward who both attacks and defends + 3 skill users. The cap for the skills is also very different, since in Aselia the higher cap a skill could have was about 10 uses, while in Yumina you already start with skills over 20 uses. You also only control one group.
I could keep listing the differences, but I'll stop here. Great game overall.