She enjoyed every second of it.
Episode 5 of Season 2 of Konosuba begins with Kazuma being dragged back to Keele Dungeon, since all the monsters around town are coming from there and he was the last person seen coming out. It turns out that Aqua put a magic circle on the dungeon that should keep monsters away, but since her magic is basically a signal light to other ones, it technically is their fault.
When they arrive they find these chibi masked guys running around, and they explode when they grab someone. Darkness just tanks the explosions and takes the lead with Kazuma while Megumin and Aqua stay behind, the former being useless and the latter being triggered from the last time. Darkness is so happy to be able actually hit the dolls that she charges forward until she finds the one responsible for it, a commander of the Demon King’s army called Vanir and chooses to go against him.
However, Vanir actually just came to check on the knight guy from Season 1 who got offed by Aqua and check on Wiz, both of whom were a part of the Demon King’s army. Since he found the dungeon unclaimed, what with Keele gone now, he just wanted to use it to troll adventurers before he died. However, since Aqua drew the magic circle that’s keeping him from claiming it for himself, he wants it gone and for her to pay.
Also, since Vanir is also a mind-reader, he uses it to screw with them and basically tempts both Kazuma and Darkness for a laugh until he seemingly gets cut down and leaves only his mask behind. The mask naturally possesses Darkness, only to find that she’s more than eager to go along with it. In fact, she’s actually enjoying it when he mentions that the longer that she resists the more painful it will be.
Kazuma just decides to go erase the magic circle (read: evidence) while that goes on before placing the sealing talisman on the mask, meaning that Vanir is stuck within Darkness until they can get Aqua to just purify him. Unfortunately, he manages to take control of her body near the end and intends to take out Aqua before she knows what happened. But it really doesn’t matter much since Aqua senses him coming and tries to exorcise him on instinct.
Vanir actually calls her out on etiquette, revealing that Aqua has a cult based around her in the process, before everyone tries to grab Darkness so they could free her from his control. She doesn’t try too hard to resist him; in fact she’s basically getting aroused by having all of them trying to come after her and actually urges Megumin to hit her with an Explosion spell just for the chance to take it.
This fortunately results in Kazuma being cleared of his charges and debts, since a spy wouldn’t off one of the Demon King’s commanders, while Darkness is commended but is embarrassed since everyone knows her real name thanks to Kazuma. So all’s well that ends well as the episode ends.
Darkness… oh Darkness…. The masochist in her is strong in this one. Not only do we see her tank status in full effect, but she actually has some kinship with Vanir at the end. Then there was the way he was trolling them left and right the entire time. I had to laugh, which is a good sign, and the art was reasonable again without the constant jiggle of the last one.