I understand these character similarities might be arbitrary, like M and W being flipped. But it's tripping me up enough times that I thought if I knew a reason, perhaps it would help me memorize these characters.

ち (chi), き (ki), and さ (sa) are also similar, but they are actually different. Though I think I would have preferred ち (\*sa), き (ki), and さ (\*chi) so the direction of the 5 would characterize the "i" sound. Sadly, it isn't consistent. ¯\\_(ツ)\_/¯

So, is ま (ma) related to ほ (ho) or よ(yo) related to は (ha)? It seems the bar means the "h" consonant but the musical note does not vocalize consistently (it either means ("a" or "o") or ("m" or "y") by itself).