Jane over at 1000 Summers makes a nice catch re Tsukuba's name: the kanji for his name opens poem #13. So, like Chihaya (Chihayaburu, #17) & Shinobu (Shinoburedo, #40), Tsukuba has his own card. So, maybe he will make meijin
Jane connects Tsukuba the anime character to Retired Emperor Yozei, a violent tyrant deposed for wantonly killing people for sport--but notes that the poem is a love poem, so--my reading now--perhaps he will be another sadist who loves karuta, like Sudo.
Here is Mostow's translation of #13:
Like the Mina river
that falls from the peak
of Mount Tsukuba,
so my longing has collected
and turned into deep pools.