Riyo's naga-Kiyohime is oddly cute. Come to think of it, her being a naga, which are from Hinduism/Buddhism/Jainism, might be a reference to how the priest Anchin (ie the one Kiyohime was originally in love with and murdered) was Buddhist. Or at the very least, Anchin hid in the Buddhist temple Dōjō-ji.
I also find Olga risking death by poisoning in exchange for not making Serenity sad cute as well.
It IS a reference... to her legend. She actually returns to her dragon form briefly when she unleashes her Noble Phantasm after all, and it's a serpentine dragon. It can also be seen in her Final Ascension art and the Verse of Burning Love Story craft essences.
Oh Master~ where are you~?Masters have a much rougher job than I had imagined.I've always been so full of myself, but I'll be sure to show my appreciation for everyone's difficulties and be a good boss from now on...Ah!Director!Oh no, she's been poisoned!SLITHER SLITHER~S-Stop! Don't come over! Don't touch me!I'll suck it out for you right away!FWOOPYou're so kind...Why are you hiding from me~?If she finds me she'll cook me alive...Master...