For the challenge quest I tried out a Summer Arturia solo, the first run was only supposed to be testing the waters to see if it was viable, but it was unexpectedly stable and I didn't have to retry it.
With decapitating bunny CE to ensure I could always hit her with a buster card to lower her NP gauge, she... well, that was basically the entire thing in a nutshell. Shiki couldn't deal enough damage to outpace Archuria's healing skill at all, and she couldn't spam her own healing enough to outpace an NP every other turn. No momentum for Shiki either offensively or defensively there. The hardest part was waiting for Fujino to die so I could start chaining properly.
Unfortunately I had no luck at all pulling Shiki, although I did manage to NP4 my Lancer Alter so I'm not even mad. If I ever pull a fifth copy I guess I'll have to grail her up to 100 instead of just 90.