As you can see, you can't get this ending by normal means. You get this ending by drinking the tainted water repeatedly despite all the signs that point to it being bad.
I've read that you need to drink it atleast once, but I'm not sure and I didn't check it. If you drink all the way until it only gives you 10 EVO Genes and then stop, you will be fine and get some extra EVO to use, so I didn't let the opportunity pass.
And by the way, despite the narration making the life of a slime sound bad, the one in the picture looks pretty happy. Maybe it's because now it gets a chance of appearing in a Dragon Quest game.
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46 Okunen Monogatari~The Shinka Ron~ (also known as E.V.O. - The Theory of Evolution via its...