Welcome to the forums! I’m very sorry to hear that you don’t have access to your data. As of January 15th~, 2018, the LINE version of the application has been terminated. With that, players who wanted to keep heir data were required to make a Skullgirls account to do so.
However, to ensure that you data can be migrated to the new App, you are going to need to create a Skullgirls Login (you will be prompted to do so as soon as you open the 1.6 version of the App). You will need your Skullgirls Login in order to continue playing in the new version with your existing data.
If for some reason you do not login to Skullgirls and create a Skullgirls Login between now and January 15th, your data will be lost once the LINE Skullgirls version shuts down.
Since you weren’t here to be able to make a Skullgirls Login, your data is probably lost.
Hope is not lost, however! You can send the developers an email at firstname.lastname@example.org , and they can try to help you. Be sure to give them as much information as possible as to what was lost.