EARLY WARNING i've only just gotten into tama so my logic will be all over the place... and some of this is for fun and silly, inaccuracies abound.

KEN & KAZTCHI

rolls over and dies. ken consistently gets the Best Possible stats, maxed out, always playing with him, feeding him high quality food, cleaning up after him without complaint or 'eww' at the toilet humor... if ken was a gamer he'd be disappointed in always getting the same tama ╮(︶︿︶)╭ some experimentation is needed. kaztchi would destroy his sleep schedule and there'd be 0 regrets.

the only time i can see ken "neglecting" kazutoshi is study hyperfocus & quiz shows. he forgot to put him in daycare before a long sesh, or an appearance. dude would be so devastated to see the care mistake. LET HIM UNDO-!!!!!!!!! KAZUTOSHI!!!!!!! (banging his fists on the floor).

scary world: ken gets into genetics gameplay and selectively breeding kaztchi to get the "best" kaztchi. i... that's too intimidating... the implications... not to say i don't want to draw the ideal kaztchi now. i do. fuc

alternate to all of this: one of those AUs where the virtual creature breaks the game. this would be kaztchi being effectively immoral, incapable of marriage, will never leave behind eggs, etc. basically a virus. i imagine this as a bootleg or cracked... perhaps like, anti-virus malware. buy a knockoff, get cursed with the same miserable tamagotchi over and over. ken of course would love him dearly -? if anything he gets attached to his oddities. how selective and expensive his diet is. easily unhappy, easily hungry, doesn't like the toy you're playing with him, beeps at you every half hour only to deny whatever you've given him. to ken this is slightly overwhelming but "he just wants my attention ＼(≧▽≦)／ isn't that wonderful!!!" mao, exhausted of the beeping "mh..."

KAZ & KENTCHI

kaz meanwhile by virtue of being sickly and inconsistent sleep/energy levels, neglects his tamas. not out of choice and it makes him feel bad, but there's something comforting about a mistreated tama living anyways and loving you.

kentchi would be confused at this new owner who always seems so tired., um, he can take care of himself! (starving) (doesn't beep for kaz's attention) (cycle)

this is a much simpler dynamic, hehe...