Useless? Hardly. Kazuma starts out as a shit in neet with serious unresolved issues. He squandered his life away in our world before dying and speculatively would have probably squandered his reincarnation as well…
That is if not for these three. Kazuma arrives in the fantasy world to find it is not what he envisioned or his media had prepared him for. His first acts are to join the guild and find out he is not spectacular in stats, and then work a construction job. Aqua gained the coins used to register but maybe kazuma would have worked that out alone- that said however, it is the presence of Aqua that helps attract party members since he is low level and not an arch class. We continue in with early in the story these 3 driving things ahead- often forcing the situations that lead Kazuma to progress or at times even supporting him or saving him in various ways such as when he dies and is resurrected. The company and friendship he gains from them is critical in both his mental health
/morale as well as moving along his journey. It is HIGHLY unlikely he would have ever gotten involved with fighting the first demon general if a certain member of the group hadn’t pushed him into a confrontation. It is use of their skills such as Megumins explosion at several critical junctions which allows him to gain renown and rewards for certain large tasks or just survive.
In the books certain other things happen and I’m trying to avoid spoilers to any who haven’t seen or read but basically you can see within the first season and pretty early on even how his interactions with these three push him forward but also guide his character development and bring out many of his better qualities. While his second life has frustrations and low points, he does more and experiences more than his first life and it is these three who make that possible because they are both messed up and desperate enough to party with Kazuma and become his friends.
That is if not for these three. Kazuma arrives in the fantasy world to find it is not what he envisioned or his media had prepared him for. His first acts are to join the guild and find out he is not spectacular in stats, and then work a construction job. Aqua gained the coins used to register but maybe kazuma would have worked that out alone- that said however, it is the presence of Aqua that helps attract party members since he is low level and not an arch class. We continue in with early in the story these 3 driving things ahead- often forcing the situations that lead Kazuma to progress or at times even supporting him or saving him in various ways such as when he dies and is resurrected. The company and friendship he gains from them is critical in both his mental health
In the books certain other things happen and I’m trying to avoid spoilers to any who haven’t seen or read but basically you can see within the first season and pretty early on even how his interactions with these three push him forward but also guide his character development and bring out many of his better qualities. While his second life has frustrations and low points, he does more and experiences more than his first life and it is these three who make that possible because they are both messed up and desperate enough to party with Kazuma and become his friends.