I personally feel like the visuals "soften" the impact to a degree, but yeah, yikes. And I know from Hardcore History that historically, typically the vast majority of casualties come from when a line breaks and everyone starts running away. They can't fight with their backs and heads turned, they're not organized so there's limited ability to coordinate and support each other, and the still-organized opposition just hacks into them all freely, been that way for thousands of years.
So running away is often considered selfish, since it theoretically threatens the whole group, besides abandoning whatever ideological grounds for conflict there may be.
Also, I bought the book this manga is based on, and my mother finished reading it already