Unless you explore quite a bit, you’ll probably encounter Apsaras’ side of the story first. Apsaras wants to help weak demons, but Leanan Sidhe feeds off the shattered dreams of those she instills with false hope. You’re asked to defeat her.
Once you arrive in the mountains above Shiba Park, though, you hear a different story. Leanan Sidhe wants to give demons a chance to succeed, where Apsaras is only concerned with making them worship her.
Whichever one you’re speaking with, you’ll have a choice to take their side or engage in battle, and then one more chance to make sure it’s what you really want to do.
Neither demon fights alone. Leanan Sidhe summons Ippon Datara to fight, and Apsaras has a small army of Agathion.
Apsaras is easier to deal with. Agathion are weak to ice, but Ippon Datara hits hard and is weak to only light, which you won’t have much access to by now.
However, Apsaras also less helpful. Leanan Sidhe is weak to force (wind), and Apsaras is weak to thunder, both of which the Tokyo Diet building boss has access to. Whichever you pick, swap the Nahobino’s affinities where he blocks that weakness (e.g. blocking force), and it automatically ends the boss’ turn.
The biggest difference is overall utility. Leanan Sidhe learns Media, a party healing skill. Using that makes the boss fight much easier, and you can pass it on to another demon during fusion.
Expect similar quests in every region, with similar results. For example, in Shinegawa, you’ll choose between Lilim and Principality. Lilim learns dark resistance, which is helpful against the Shinegawa boss, but Principality exploits its weakness to light.
That’s all you need to know about the big Shin Megami Tensei V Apsaras or Leanan choice and who you should choose, but make sure to check out our other Shin Megami Tensei V guides for more tips.