You know... the more I watch, the more Kai and Daidan's dynamic in Monstrosity reminds me of Spear and Fang.
In Primal (the show Spear and Fang are from), the couple has to traverse a ruthless and unrelenting world that threatens to drag them down at every turn, filled with monstrous creatures ten times their size and strength. Sometimes they can fight, other times they have to run, as the creatures are too great in size and might to take on. It's a world that resembles the Land of Monsters in its crudeness, and with a very similar premise to what Kai and Daidan supposedly endure in between the last episode of Monstrosity and the beggining of Kai's Monstrous Journey.
Both duos also meet and establish their relationship through grief. Spear and Fang cooperate for the first time in order to avenge their families. After killing the monsters responsible, they are left with no one to care for and no purpose, alone in an unforgiving environment. From then on, they form an unlikely aliance; that even with some hiccups at first, grows into an unbreakable bond between the two fighters.
Daidan and Kai meet through sorrow as well, with Daidan channeling hers into pure rage and a desire for revenge. Kai stops her and makes her reconsider, which grants him the dragons' loyalty. After the encounter with the Squid Monster, and the sacrifice of another fellow survivor, they decide to travel together, trying to survive a world teeming with monsters without becoming one themselves.
In a world where everything is out to get them, these connections are what keep these characters not only alive, but living. They are the reason the other wakes up in the morning, and the reason for which they fight to stay alive and keep themselves in check. They give eachother purpose in an otherwise futile existence.
Also these duos are both composed of stoic, strong man and giant, strong scary lizard, which I find funny.
(tldr: I think it's very cool that both these shows feature sad man and big lizard in a ruthless world fighting for survival and finding companionship in eachother while helping eachother grieve in their constant struggle to stay alive).