
Well, even if it does feel like they are rushing things, if they want to, they can do it. It happens irl too.
There's a story about a female who's in military and a guy who's a chef at the army. They got together on Wednesday, and got married on Saturday.
Means, you never know what will happen. Since they are on life and death situation.
Actually, in the old times, dating is short term and they consider marriage in a young age is normal. We just think it's weird because of our generation.

Haaa.. This is so peaceful and just collecting material leisurely . Any other manga like this? Of course, harem free!

Here's my list, it's got plenty of good stuff within the genre. Nearly harem free!
http://www.mangago.zone/home/mangalist/454568/
TRUCK-SAMA CAN YOU STO-
*gets hit by a truck*
Now be reborn as a new fantasy you... after you spin the roulette of what you'll be and draw from the lot box of your skills ^-^ Because we're fair you get 1 free re-spin and 2 extra skill draws!
Psst... be wary of the ???? results!