After seeing how disgusting this monster actually was, obviously all three of the S rankers were quite disgusted but still they were ready to join Elena on the expedition to hunt these beings. All three of them had the intention to join her as it looked like these monsters were quite powerful so holding back with their S ranker would just put the city in more danger.
But Elena rejected the idea by saying that someone needed to stay in the city to handle any unforeseen situation. Elena also mentioned that another's S ranker, Tomoe was also staying behind but still having one more S ranker would be helpful.