You all remember a part where Shiki is wandering around the house, looking at the carved names at various spots: Shiki, SHIKI, Akiha, Shiki, Shiki, Akiha, SHIKI, Shiki, SHIKI (or something like that) and thinking that as a girl Akiha must have been weaker than him, so he can carve down more names.
But, it is only in romaji that you can mistake Shiki and SHIKI. In kanji they are very different. 志贵 and 四季 for Shiki and SHIKI. So how Shiki (nanaya) not notice it, and wonder if there was another person by the name of SHIKI?