The same thing that makes them believe they are the best creature ever and other delusional and baseless crap.
Remember those pics of the Reimu and Marisa thinking they were DBZish in their mind while in reality they were only puffing and lamely body slamming? Those are yukkuri standars in the work.
I call it standars because it's what they are, basically they have this idiotically and nearly impossible low standars that make them believe that anything slightly being over them makes it something great, as long as it's a yukkuri because they clearly won't awknowledge non yukkuris outclassing them in everything ever. The irony is that, while they have damn low standars for outstanding stuff and all, they actually outclass such standars in general, which leads to them having the wrong assumption they are "that great" reason why yukkuris can be so arrogant about their "Bland Cuteness" or their "weak ass jump" or their "slowass speed" because at the end their standars are even lower than that.
JIE, until you learn to organize your ideas and sentences, your posts will remain a jumble of incoherent thoughts.
You're thinking about this too much and Funk is thinking too little. How did she get aroused by reimu in the first place? Well, duh, it's because reimu wasn't that fat before she got pregnant.
To us reimu is a blob before and after but marisa can see the difference in terms of yukkuri proportions. Although, it might be the artist's oversight. You see, human males are hardwired to be attracted to wide hips and large breasts because those females would be better at child-bearing and rearing. But once they get too fat those features get hidden behind layers of fat and the person is perceived to be unfit. In other words, humans are attracted to certain shapes which denote physical fitness and when those features are obscured or not even there in the first place, the fitness of that person is judged to be lower.
However, in the yukkuri world, a yukkuri being fatter wouldn't make it a bad mother. Quite the opposite, a fatter yukkuri would be able to better sustain its kids during gestation. Therefore, a yukkuri would be more aroused by a fatter yukkuri than by a smaller one. Also of note: being fat wouldn't necessarily make a human a bad mother but in addition to fitness a slender form also shows youthfulness, which in turn affects child-bearing ability.
This is all a moot point, though, because yukkuris aren't under the sway of "evolution" anyways. Instead, they can be explained by the theory of Spontaneous Retardation.
Well let me try to put my idea with a better rephrasing.
They have a very low standar for their tastes, at least between yukkuris.
Reimu may had not being fat back then but you have to consider that she was always dirty and smelly, so this Marisa is basically doing a paralel of someone having sex with a hobo out of a whim. Yet yukkuris do the whole "pet screwing stray or wild" quite often, why? because they have some darn low standars, which i suspect are also influential in their views of the world or their capacities.
Hmm , I think SUN just called me a moron , herp-a-derp :-o ^_^ Seriously , I am just making off-hand comments here. To clarify what I was alluding to: Yukkuri are all fat , round blobby-things without any sort of defined anatomy. Therefore it's hilarious when they call each other fat.
yet you know what's the funny thing? aside of peni lowering, Marisa doesn't look that repulsed, instead she looks like wondering or intrigued by the reimu's "sudden" Fatness.
In b4 "All the filling needed to think goes to the peni peni, the same way a lot of blood go to the penis for humans, because of that if a yukkuri start thinking they retrieve the filling from the peni-peni"
Ironically that may explain why Rapist Alices are so retardedly rabid, they plainly had lose their thinking capacity because of being in a state of constant boner.