replied to your post “The new chapter of OnePunch-Man has convinced me that Flash is not a...”
In the webcomic, Flash wears typical Sengoku-fiction ninja wear though! I don't know how much of the webcomic you've read if any (the original by ONE, not the online manga version of Yusuke Murata) but he uses some of the same techniques as Sonic (like Wind Blade Kick). Murata often changes a lot the designs for the online manga version (not the webcomic) to the physical version for sale ha ha look at how Stinger change for instance!
They often change it to make it more similar to ONE's original designs before the volume is out for sale. Notice how Flash used to have really long hair many chapters ago and in the manga, but now Murata changed it to much shorter hair like in the webcomic (for Sonic, they devised the excuse that Genos cut his hair, and now he looks like webcomic Sonic again ha ha)
Flash has very long hair in the anime and in the first panels of him the manga adaptation, back before Boros's attack, I meant XDDD
I just found how to reply in tumblr and it’s so goddamn complicated X~X.
Well, it’s just pure my theory and speculation. Sonic said he is from a ninja village who trained from childhood. Flash doesn’t seem like a ninja to me, his wardrobe draws attention with its brights colors unlike a ninja who usually wears apparel of dark hues like Sonic’s.
Flash speed run produced shockwaves in chapter 104 whereas Sonic never made shockwaves on par with what he produces becacause Sonic is (supposedly) a silent assassin. We are no longer a ninja if we produce a tornado while moving.
If we look at the last pic that I’ve posted, Flash sword seems longer than Sonic. What Sonic uses probably is ninjatou (ninja-sword) which is shorter than regular katana. Here, it is stated that for convenience the ninja would choose a blade that was shorter and straighter than usual. Flash likely uses standard katana.
I’ve read the webcomic (up to the fights with Garou). Yes, Flash is more like a ninja than in redrawn manga, but during his fight with Garou, it seems that he didn’t bring any weapon other than his sword (which is already broken by Saitama), that is why he used bare-hands (fists) instead, unlike Sonic who usually brings typical ninja weapons like exploding shuriken and kunai. His fighting style is very similar with Sonic and yet is very contrast too. We can say that perhaps they had trained with the same master, both are specialized in speed and got the same speed techniques and moves but decided to create their own styles and do it with their own ways instead.
ONE and Murata, please stop teasing us, I really want to know what kind of relationship they have!!! >.<