A comment on what I think may be a mistranslation on page 34, panel 1: Honda is talking about object fetishism. This does not refer to a fetish in the sense of it being a sexual kink, but the practice or belief that physical objects possess some sort of supernatural powers. The term originates as an European term for objects used in West African religious practices, voodoo dolls and other idols (in the sense of religious or spiritual icons or tools, of course). This term is much more rarely applied to European or Asian religious iconography such as prayer beads, Christian relics, Shinto shrines, et cetera, though a post-colonial view of the definition could certainly be applied here. Historians, economists, and psychologists reapplied the term in other contexts, such as Marx' theories of commodity fetishism, where the object (and the circumstances of its production) is ascribed economic value (a barrel of petrol is worth so and so many dollars, rather than how many hours it can fuel a generator; an employee's worth comes from their contribution to their employer rather than their contribution to society or any inherent worth as a human being), or Freud's... odd ideas that as best as I can tell revolve around either developments in parental relations or assertion/affirmation of masculinity (the pick-up truck, the unnecessarily high-caliber firearm, the collection of fandom memorabilia, etc.).
In Honda's case, however, it's more accurate and useful to point to the far less esoteric concept of the imaginary friend. It is somewhat worrying that Honda manifested Ryuu to cope with her social anxiety, and as a teacher Takayanagi should at the very least have suggested visiting a therapist, but as a coping mechanism it isn't on the whole negative, and I can also respect that he sees how it has helped her be good and how he chooses to commend her, even if I don't think it's the healthy way forward in the long-term.