OMG it's true!
I have reread this a couple of times and never noticed! Thank you!
Dont.get me wrong I like their relationship and all and I would be ecstatic if he was just as you said pregnant but maybe he was just wiping his hands..
I would have thought so too but it's how they acted that gave it away. We can assume that Jin's a very protective person, especially with what he nearly did to Itsuki, but he wouldn't say "be careful" to Itsuki if he's just a stay at home right? And if he was indeed wiping his hands, then why only wipe one hand? and what more, the extra showed that they followed old traditions where they have to consummate their marriage and also they did it when Itsuki was in heat.
I didn't notice it the first time because this part was too rushed that I got wiplashed by sudden weddings and them living together vut holy macarioli!!!
Itsuki is actually pregnant here!!! Look at that curve where his hands is holding... there's also like lines beside it like "surprise". And the fact that Jin said be careful to him and Itsuki was the one who answered "I will" while holding his tummy... Well... I'm blind.
http://www.mangago.zone/read-manga/kasegimasen_kara/mf/tr_chapter-5/pg-46/