Chika Anzai and Wataru Hatano? Seriously? The contrast between their voices makes this impossible to take seriously. He's a straight-up basso profundo, and she's ridiculously squeaky. To be honest, I'd always imagined Kirie as having a deeper voice, considering this supposedly takes place somewhere between 1940 and 1960--which means the 'cute voice' wasn't a trend yet, so if Kirie had a Chika Anzai voice, people would've thought, 'what the heck is wrong with Ms. Goshima's voice?'
Also, Shuichi is a pubescent boy. It is highly unlikely his voice is like that.