if you refer chap 16 when todo asked megumi "what's your type" he didn't asked what's your type of woman but he asked "what's your type" and megumi answered in chap 17 "why do I have to dicuss my taste in women?" that panel made me think why did megumi answer that when todo asked "what's your type?" so then todo again asked "answer me what's your type of woman I don't care even if it's a man" that's when todo mentioned women then only megumi answered "that person" and in chap 18 while megumi and todo is fighting todo said "so flimsy, both your body and your taste in women" true megumi said it in a gender neutral way but maybe todo did assume megumi was talking about a woman. and also if you noticed after megumi answered "that person" mai and nobara's reactions make it seems like he's talking about a woman. this is why from just "that person" answer we can't prove he's bi/pan and it'd be better to get the confirmation from the author, read chap 16-18 again and tell me what you think too!
Guys is megumi bi?