Apocalypse Summoner was the first summoner novel I read. At least I think so, the links to the story no longer exist and I don't feel like searching an aggregator site for it right now.
There are girls liking the MC, but he moves around constantly to get stronger so they are minor characters. The MC doesn't return their feelings either (if he is even aware of them). I DO know that there is some chemistry between the MC and this doctor girl. However, they both are the type to focus on their goals. So, from up to where I read (I'm not current), they acknowledged they have feelings for each other and went their separate ways. Training takes priority over all other things. The fact that one of the MC's best soul pets is a ticking time bomb is a big plus! It constantly absorbs his power and if it is not fed enough, it will attempt to eat his soul instead.
Not really summoner per se, but MC have several pets that he brings around, like pokemon minus pokeball.. Monster Pet Evolution Friendly warning, the story contain some degree of what do we called it again, author country is da best type element.. And rush ending, aside from that the story is quiet nice imo as there's no romance even tho there are several female characters who are kind of close to MC but all MC care is how to exploit his slaves, ehem I mean how to take care his pets
is this the story where the moster taming only started for 3 years but the author forgot about it and add elderly expert with decades of experience.
yup that's the one.. The grandpa kinda stranded in the chaotic space/island and somehow get op pet and skills