While I still do enjoy this manga a lot, people have become a little too comfortable with disrespecting Frieren by needlessly comparing this manga to it. Guys, both of them are trying to accomplish separate things with their respective stories. That being said, Frieren will always be the golden standard.
I feel people are wrong for comparing them, sure both arguably are using the same theme of Mono no Aware, but I feel they're doing it in too completely different ways to really put them side by side
Although Frieren has the obvious Mono no Aware due to always showing her past with the former hero party, with one big point being how she actually did love Himmel too but her autistic elf brain didn't let her notice it and disappeared for decades and lost her chance to be with him, I would argue the series is mostly hopeful because it shows the world they created and how life continues thanks to their efforts, it keeps showing us the happy times that passed but the series still focus on the present.
This series meanwhile I argue do the opposite, for the most time we see Aesir shenanigans as he travel and learning the wonders of other cultures, but unlike Frieren he's completely disconnected from other people, with years for him being like weeks, he's living at his own time rather than living in the present, without fully understanding how everyone he meets is effectively a one time thing only due to how long he travels and stays away.
While Frieren is hopeful and
really lives in the present, I feel this series has a permanent sense of melancholy in the background, sometimes we get distracted by Aesir having fun and maybe he's either in denial about it or his high elf biology that helps, but he didn't really realize how much he's losing by moving again and again.
Rather than living in the present like Frieren, I can't help but feel we're not seeing Aesir living in the present, but rather him remembering his past after living for a literal eternity, which is why there's this constant sense of melancholy and perhaps nostalgia.
Frieren shows us the happy times she can have by living with humans at their own pace, even though she's eternal and her time with them is nothing compared to how long she already lived and will live, this series meanwhile show how everything and everyone is like leaves to the wind for a immortal, and how he's fated to see everything change and everyone he loves inevitably die, while he continues moving on, forever.