So here it is, Fate/infinity crisis. Or that is pretty much what it is.
First of all, since the anime is nothing but advertisement and a celebration/mourning of the death of doctor Roman, I will be talking spoilers for the game. If you are just going to watch the OVA, I gave it a 5, it is average, some nice fight scenes (Okay, ONE good fight scene), overall, none nasuverse fans aren't going to understand anything. And regular watchers can stop now, as for all you other curious people who don't understand anything about what is happening and want to know, full spoiler train ahead.
---------------SPOILER, ROMAN DIES, SPOILER-------------------------------------
Fate Grand Order, is the combination of all fate series so far, apocrypha, extra, zero, sn, etc. it is the fate franchise version of the infinity crisis and the largest, LARGEST work yet, both in scope and storyline. Unfortunately some of the early writing was handled by Sakurai (WHO WE DON'T SPEAK ABOUT!), so it leaves a bit to be desired, but most of the story is actually fine and far more grounded than zero and FSN (no more muh ideals)
The story is, the Nasu parallel multiverse is ending, because "someone" or "something" destroyed the linchpins of human history (also called quantum time locks) and incinerated all of human history. The only organization left is Chaldea which is left drifting in a fractured uncertainty of history, the last of mankind, with around 20 people left. But have no fear, as Chaldea is a super organization established by Marisbilly Animusphere, the only human magus in the history of nasuverse who won the grail war of his timeline and actually made a wish that isn't stupid. (infinite money to build his super organization, my god, someone stop this man before common sense overflows nasuverse!)
So with the infinite money he got, he bought magic and technology from all the different magus and science organizations around the world, salvaged the fuyuki summoning system into the FATE summoning system, inducted talented people of all fields together all with the intention of ensuring mankind future. Such amazing common sense and action, SEE, this is how you become the ally of justice Kiritsugu.
So basically Chaldea is the fate version of the avengers, the storyline follows Chaldea's journey travelling into singularities in the past to fix history as they face off against unprecedented threats in the Nasuverse, along the way, many heroic spirits would be met and long story arcs with each servant would follow.
Regular viewer: But wait why don't they just use time travel to make sure the bomb doesn't go off? (I am so much smarter than the author)
Don't worry self inflated viewer, cause that doesn't work, I said messed up history remember? In the nasuverse you can't actually change the past, cause if you do it you just end up destroying the timeline and you all die anyway, which is what happened here, someone forcefully changed the past resulting in the destruction of the timeline and Chaldea is there to remove the source of the problem. So you can't actually change the past, so any time you feel like "time travel would easily solve it", you are adding to the problem.
Overall, FGO is perhaps the most grounded storyline yet, why do Chaldea save the world, unless you want to cope inside the facility and play ping pong with Da Vinci for the rest of your life drifting in a sea of quantum uncertainty, you have to save the world. The characters have growth, steady growth from living and talking with people, no empty philosophy debate like in zero (king's banquet). Overall, it is fate living up to what its truly is at its root, it is a shounen, a slightly dark and occasionally pretentious one, but a shounen none the less. Most of all fun (Okay, not the Gacha, that thing is cancer).
Overall, if this anime grabbed your interest, take a look at the game (Skip Sakurai's part) and the story, it is a good entry into the fate franchises and better than zero and SN in some parts.
