Is there any resource for old manga, or is it not going to happen?
I watched Submarine 707r and was disappointed by the fact it was not concluded.
And if you reccomend Blue Submarine no. 6, I will kick you in the nuts because it is shit.
Nana Toshi Monogatori also falls into the category of having an amazing 2 episodes then just fading off the face of the planet. But I have no idea if that was based on a written work.