"The greatest assassin on Earth knew only how to live as a tool for his employers—until they stopped letting him live. Reborn by the grace of a goddess into a world of swords and sorcery, he's offered a chance to do things differently this time around, but there's a catch...He has to eliminate a super-powerful hero who will bring about the end of the world unless he is stopped. Now known as Lugh Tuatha Dé, the master assassin certainly has his hands full, particularly because of all the beautiful girls who constantly surround him." -Yen Press
SPOILERS BELOW
- - - - - - -
I suppose most isekai reincarnation series will have a younger original character to avoid an older person mentality, but this isn't particularly novel either. At least it's easier to explain why he would have good skills if he was a real veteran already before dying. Other than that, it seems strange to take down a whole airplane full of civilians to kill a single person. We know from the incident when the Russians shot down the airplane above Ukraine that the investigation will always be beyond thorough. I wouldn't want to be the pilot of the fighter plane. That dude would soon be neck deep in shit. It would have been much easier and less of a headache to assassinate just the old man and nothing else. The author clearly got ahead of himself here, right at the very beginning.
Hard to say anything much about the story otherwise. It seems to be bloody. It has an annoying goddess. That's about it.