!Spoilers!
Also I have never uploaded something with this site so I am not even sure if the save is in that rar. If it is not I am sorry.
Okay, so there's extra content after you beat the main villain i expect you to know the game for the most part for this walk through if you have not played the game it wont make sense. ill explain steps as well as i can remember and ill also be adding the save file of the game completed.
1. to start these you have to rest in bed at hometown, option will be "dissolve party" or something like that.
2. sister will disappear and leave note behind, read that note.
3. Head to annas house in central city, she'll say shes going to visit talom.
4. head to city with the secret underground base, i think its called fiscal? but head to secret base and head to the leader, where you will spy on anna and talom. short cutscene and then follow them. (save now)
5. after following them click on room to the farthest left, a cut scene will play and after they will leave the room. (was a bit buggy for me but keep trying the scene till they leave the room or reload the save just in case)
6. go talk to talom, then head back to annas house and recruit her, also go recruit the squirrels farni and flora.
7. head back to taloms place and talk to him, queue cut scene, then head to basement teleporter.
8. go past dung where annas was captured, into the castle spirit place.
9. go up till you meet angels and through the portal into the next area, be careful its tough down here.
10. reach your way to the final boss while you have cutscenes of your sister playing after each fight.
11. when you fight the final boss, do not attack your sister. its hard but you need to kill everything apart from her, otherwise you will beat the fight but you will get a game over screen after the fight.
12. save here, and talk to sister at your home by showing here red ornament found in elders house. go through dialogue till you have cut scene, i cant remember how it goes so load the save earlier if you mess up.
13. after scene go back to where farni and flora are, talk to flora and she'll tell you farni is up to something in central city.
14. go to annas house and talk to boy, then head to the lab and make your way down. till you find the two.
15. head back to annas house after cutscene, and talk to boy at window, dialogue here should be obvious.
16. after this you can head back to hometown and talk to robot and receive the last piece of the gallery area.
Theres still more fights and areas after this, but this is just the ecchi stuff, explore and find the mini bosses. which might be something you need to even get the last gallery piece, i am not too sure exactly.