You know what I never got?*SPOILERS*

Did she really know Leon that well, though? At one point, before their memories were erased, perhaps, but she seemed to stay away from the others during the game. And I'm sure he would not have been the only one who might show up that she'd have a better chance at killing.

I don't really think Hagakure comes off as that righteous. Wasn't the letter about a way out or something? I could easily see him falling for it at that point. He actually is the one who gets killed in the demo version of the first case, though we never do learn who did it.

Hagakure? Common sense? My mind simply cannot process these two things together.: P

I think Hagakure, especially before anything all that bad has happened, is at his most oblivious. And he went along even after all those murders, to meet up with Sakura. And this was someone he had no trust at all for. And would a panicked Sakaya honestly think the clueless one would refuse?

Even going with the idea that she didn't plan it out well, doesn't that only support that she would not have thought much about who she picked? In that case, wouldn't her mind have immediately jumped to weaker prey?

Well, about the planning thing, she probably knew about basic things but not like who exactly to murder. Like she planned that she would frame Naegi by committing the murder in his room - and that's why she picked a guy, I think. Because it would be unlikely for 'Naegi' to invite a girl into his room to 'murder' at night. Besides, why would the murdered girl agree to go to 'Naegi''s room?(As in, if Sayaka successfully committed the murder and pinned it on Naegi.)

(Actually even if it was a girl, I think people would have still believed that Naegi was the murderer. But I suppose it would be even more believable if it was a dude.)

But anyway, from the guys you have - Ishimaru, Mondo, Togami, Yamada, Hagakure, and Leon. Togami's out of the list already, because he was hostile right from the start. Mondo's a no, he could easily fight back against Sayaka. Though Ishimaru and Yamada are weaker than Mondo, they too expressed fear and were nervous about the whole situation. Leon was nervous too, but at least his first impression made Sayaka think that there was a higher possibility of him turning up in front of her room than Ishimaru/Yamada.

So why not Hagakure, who didn't believe in the school trials in the first place? Remember - Hagakure was different at the start and lacked "character development" (as he said so himself...) so he didn't seem as dimwitted as he did towards the end. Who really knows if Hagakure was really that dumb from the start or just didn't show his stupidity right away.

No one knew that Hagakure was serious about the whole "this is a joke" thing until after Sayaka's murder. Everyone thought that he knew serious shit was going down. But he didn't. They all realised that Hagakure was a little dimwitted /after/ Sayaka's death, so Sayaka wouldn't have known so much about his stupidity.

So for Sayaka, who didn't know much about anyone, she would have to pick between: The weird fortune telling guy (who she didn't know was dumb at that point of time) VS the jock guy. Of course, as she is a pretty idol, picking the jock guy would be a better choice. There's more of a reason for jock guy to visit your room compared to the weird fortune telling guy.

Jock guy would be a better choice because there was a higher chance of him having the hots for her (being a pretty idol) than weird fortune telling dude. Some girl you have the hots for invites you at night? Obviously you're gonna let your guard down. That is, if you're Leon. She took a risk, but it wasn't as big a risk as calling any of the other boys instead.

(my thoughts are so messed up i'm sorry)

The manga also gave her and him a brief interaction that ended in him inviting her for some tea, and she chose him because she thought that he'd trust her enough to come by. Even without that instance, I guess he'd be the most likely to follow the note among all the guys for already mentioned reasons.

Also as far as Yasuhiro vs. Leon, Yasuhiro's a pretty big guy! Obviously not as built as Sakura or Mondo, but he's still tall and he's got a wider frame than the other guys (also barring Hifumi, but...Hifumi). In a violent situation, someone that size would be intimidating for someone petite like Sayaka. Leon may be an athlete but he also doesn't necessarily look like he's built just for raw power, and Sayaka assumed that she'd just be able to get one off-guard jab in with her knife. Trying to do that swiftly to someone of Leon's size and muscular build seems easier than doing the same to someone naturally wider-looking who's got a good two heads on you in height.

I think a lot of the motive in choosing to frame Naegi was simply his whole "I'LL PROTECT YOU MAIZONO-SAN I'LL MAKE SURE YOU GET OUT OF HERE ALIVE" so she probably figured she could tell him something like "You promised you'd get me out of here NO MATTER WHAT, so take this fall for me" It also helps that they didn't know about the execution rules at the time, so she wouldn't have worried about the moral implications of letting everyone else die so she could leave.

I dunno man, it could be a guilt thing just as well why she didn't choose a girl? I dunno much about Japanese culture but even just generally speaking, because women are seen as ~vulnerable~ it's also seen as somewhat more deplorable to kill a woman, especially with such a cheap trick—Sayaka does care a lot about her image (not that murder is the best thing for one's image, but we saw how irrational she'd gotten by then). Aaaalso, thinking about it, Naegi's a really wholesome guy! He gives that impression from the start. If she's trying to frame him, it might be hard for someone to believe that he was inviting a girl to his room just a day in, because that has a more less-than-savory implications than the alternative (it could also be an attempt at holding up his image, a little—again, not completely rational, but Kyouko does say that she probably still cared about him and had inklings of doubt about throwing him under the bus from the start).

And as a relatively petite girl (notably taller than Sayaka but still with a body type made of toothpicks), if I had to pick someone for that kind of plot (oh my god this is the weirdest hypothetical I've ever put myself in, please don't call the police), I still think I'd pick the lean, almost scrawny still-an-athlete over the generally really big dude. Baseball's not really a sport built for raw muscular power. It'd be easier for someone like me or Sayaka to get quickly and effectively swatted aside or broken in half by someone big and strong looking like Yasuhiro than someone specializing in a sport where players are mostly made to be more agile—hitting hard with a bat doesn't necessarily translate to having that same strength behind attacking a person when you're off-guard and weaponless (or, y'know, presumed such).