if we're speaking of kanae's yandere potential then wouldn't knfw be the best? www fuwa's innocence paired with his incessant babbling make for a clean middle ground between knkz and akkn; his unfamiliarity with kanae lets him banter freely in a way that akina wouldn't dare to - yet he shares the same readiness to believe kanae's teasing and tricks. a perfect fit in my opinion LOL.
not to mention knfw has more room for flexibility as it's not deeply embedded in lore enough to get caught up in 1 trope, but if we're going with the yandere approach, his naivete could be twisted into blind belief and reach a point where kanae would convince him into total isolation from anyone else. again, if we're talking yandere potential, i think situations where possessiveness has no limit are seriously the best lol. might as well go the extra mile, right? that's not to say knkz or akkn are bad, per se - it just frustrates me to see the lack of anything else.