Also, since ver1.05 is out I feel safe to put out a couple map mods I've made.
Drop these two map files into your unpacked Data folder, they will rewrite the files for kozue's room and the entry hall for the first tutorial castle dungeon.
There will be three kozue avatars to interact with in her room.
Bottom one in bloomer cat cosplay allows you to put any girl in fertilized status, it takes around 4-5 ingame days for implantation to succeed, if it succeeds kozue will get a phone call from the girl at the end of the day or wake up the following morning and get a positive on her pregnancy test. If it fails you can just try again.
Note that in 1.02 at least, if the noncombatant black haired girl phones in her pregnancy, for some reason she did not receive the pregnant status, so the last option there is to manually give her pregnant status. Don't use it before she calls kozue though as it will crash the game on sleeping.
Middle one in normal clothing sets a girl's pregnancy progression to just after implantation in case you don't want them to have a pregnant belly just yet, as being in that state prevents the girl from going to school, cutting them off from possible hscenes and in the case of kozue, free stats.
Top one in maternity clothing sets a girl's pregnancy progression to immediately trigger pregnant belly, everyone else but kozue will immediately phone kozue as soon as you try to go to bed that day, and kozue will lose the following day from going to the hospital. Once a girl is pregnant she will no longer show up at school and will lose access to all hscenes related to the school, but will still be in town on weekends and other free days. If kozue ends up pregnant every day from then on will be a free day but you will lose access to a lot of hscenes.
There is a naked kozue avatar in the entry way of the castle dungeon, interacting will allow you to remove the clothing restriction from all pregnant party members, allowing you to swap their clothing. Only naked, with underwear, and maternity clothing will show the pregnant belly difference though, and the restriction will just be reapplied the following day anyways so not a whole lot of point there.