Not all of these choices may matter (i.e. battle choices may not impact your ending), but these are the decisions I made in-game to get the ending for this trophy.
*** Spoiler - click to reveal ***Prologue
(What should I do??) - Use knife
Chapter (Quest) 1 – Part 1
(But…) – Play harp
Chapter (Quest) 1 – Part 2
(Bravado… No, it’s not that. I think he just didn’t want to worry me.) – It wasn’t him. It was my fault.
Chapter (Quest) 2
“No, it’s…” – I’m just a little embarrassed.
(It’s not that… Oh, what do I say…?) – It’ll actually make me more nervous.
Chapter (Quest) 3
(Adjust to my pace…) – I’ll do everything I can.
(I have to do something, too!) – Use bow
(Astrum…) – I was thinking the same thing.
Chapter (Quest) 4
(It did hurt to hear, but…) – Please let me stay here.
(This is the last fight of the quest!) – Play harp
(He did it!) – Use bow
(What do I do? Astrum looks like he’s in trouble…) – I’m sorry, Toru.
Chapter (Quest) 5
(I have to say something.) – I can’t help you.
(No! He’ll die at this rate!) – Increase ally strength.
(At this rate, that person… Demento… He really might die…) – Astrum, stop!
Chapter (Quest) 6
(No, that’s not true…) – You’re not at fault.
(D-Do you… l-like me?”) – Yes, I do.
(No… If he fights that person again…) – Don’t push yourself.
Chapter (Quest) 7
(That person is asking if I’m willing to fight with him…) – I’ll fight with you.
After you make the last decision, the end of the game will play out, the credits will roll, you'll view an after-credit scene, and the trophy will pop.