Another shout out for "Thus the JSDF Fought There!" or "Gate - Jietai Kare no Chi nite, Kaku Tatakeri Manga."
The premise is a portal opened in Tokyo leading to a fantasy land. It focuses on a certain 2nd-lt of the JSDF who was sent there as part of the exploratory contingent. The strongest aspect of the manga is story unfolds in a realistic manner. If a gate to a fantasy world were to suddenly open in our world, I can realistically imagine this is how events would unfold.
This manga would win the award for the most unlikely combination of subjects on a page.
- An F4 Phantom next to a panel with an Elf girl waking up from a nightmare? Check
- Modern artillery vs the Lannisters? Check (this turns out exactly like how you imagine it would, poor knights)
- US president and politicians being their greedy self, plotting to take control of the gate and the resources beyond. CHECK
- A 700 yr old goddess of war who has the appearance of a loli wielding a great axe, appearing in japanese parliament being asked how old she is? Check.
- A battle between a 700 yr old immortal loli goddess of war against a US navy seals fireteam? CHECK! (This turns out exactly how you imagine it would. Poor soldiers.)
- A princess of such fantastical world, being sent to Japan as an ambassador, and her reaction on first encountering a BL doujin? CHEEECK (this turns out exactly like how you imagine it would. poor princess)
BTW, don't watch the anime. I hear it's a bomb.