@icarushector Mom is trying to hide even to him Kuro's nature, but he
does know to a degree, he saw her hand turn in a draconic one in the past and they discussed about her condition with Kuro herself and that it happens under excitement, so Kuro isn't hiding it it from him. He doesn't have the confirmation yet that the Kaiju is her (while definitely he has reason to think so anyway), and it's not a given that she would hide that from him and it might just be that they simply didn't talk about it yet as that degree of transformation only happened recently
Also this reminds me to tell
@ascriptmaster that maybe Mom's line at the start of page 5 should be changed into "What makes you so sure that it's a she?" as the discussion in that page is her asking how can he tell that the kaiju is female, rather than asking him if he's recognizing the kaiju as a person in particular