If I really have to explain, Fate/Grand Order is one of Japan's top popular JRPG mobile games and is about time traveling. Also it's the best mobile games I ever played because of the nice deep quality on-going story (especially it's written by Nasu; who is the author of the original Fate/Stay night) compared to a majority of other JP mobile games with just basic stories. In general, I've been a big fan of the Fate series.
So I'm very quite behind from the latest story arc due to mainly focusing on special events (and from currently being semi-active). But hopefully, I'll do a big catch up eventually. Here's my London arc gameplay.