Soshu

traditional samurai weaponry

I know a few people wanted to see the sword explored more as a character, and that in Romance Route Takumi can hear it speak (implying it actually is alive,) but a talking sword seems contrary to the tone of the story so I’d stick to the interpretation of it being the imaginary friend Kyoshika created to cope with her loneliness.

The sword “talks” to give Kyoshika the attention and affection she never finds from anyone else, to be a voice for things she’s too embarrassed to express herself (e.g. its raunchy taste in manga,) or even to be a voice of conscience. Many of the sword’s more exaggerated traits can be read as Kyoshika externalizing thoughts she’s uncomfortable owning outright.

If in the “ronin route” Kyoshika is able to form a more meaningful connection with others, she might come to express these things in her own voice instead of assigning them to her sword, though she’d still hold it tight as her trusty weapon, keeping the memory of when it helped her through her darkest, loneliest moments.