Heyyy! Sorry I took so long to reply, I don't view the forums regularly.
I was thinking about mentioning the "vanished" characters in the cast page, but I'm loathe to do that, since the comic is assembled to try and make a cohesive plot, and in all honesty, those characters didn't contribute very much to the storyline.
What can be easily done, though, is putting a question-and-answer in the FAQ that'll name those characters and link back to your Tegaki pages. Would that be fine?
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"By the power of truth, I, while living, have conquered the universe."