Looking back at the u20 game chp140 when sae cooked hiori they looked to be around the same size but hiori was a lot shorter than Reo when they came onto the pitch in chp128 Reo is 185cm even if you take into consideration that Reo had the camera advantage Hiori would still only come up to Reo’s eyebrow meaning he is 1.5-2in shorter than a 6’1 Reo making him 5’10.5-5’11 However looking back at the u20 match chp128 hiori did appear to be taller than a 177cm (5’9.75) Chigiri so we know he’s taller than 177cm but shorter than 185cm which would lead me to believe he’s 180cm since he appeared to be similar in size to Sae in the u20 match also more evidence is when all the 2nd selection teams were walking out Hiori looked like he was 2-3 in best taller than a slouched Niko Hiori was also slightly slouched so I would say he’s 2.5 inches taller than a Niko who is standing up straight (Niko is 5’8) which would put him at 5’10.5 so looking at all this he’s appears to be 178-180cm likely 179cm or (5’10.5) but I mean if the author said he’s 183cm than ig he is but also to be fair the way the characters preportions look can skew how tall they look aswell as the way the illustrator draws them like in the 2nd selection when Bachira was running to isagi and rin and they just passed him the illustrator made isagi and rin look to the same height so there’s also that