According to the spoiler pics, shukichi asks shuichi "where is Mary kaa-San".
But shuichi refers to her later as "kaasan"
Does that mean shukichi is the foster son of Mary? why would a son call her mom using her name.
And it also seems like Mary was hiding from the BO in England. But since she's now in Japan, that too shrunken, she must have confronted BO at some point during these ten years. (I'm not considering shu's fake death as her reason to come to Japan)
If this is the only family interaction, then shu wouldn't know that she's shrunken.
P. S. Masumi's love for sh-uni is so pure <3