But Katie was shown vented to her gal pals how Derek could have "a little bit more game."
"Because I kind of like initiated it [our first time]," Katie revealed in the clip. "I don't know. Maybe I gave it up too soon and he's just kind of like not really going for it -- not really making an effort."
Unfiltered host Jamie Otis asked Derek if watching that episode back was the first time he had heard Katie's honest thoughts about their sex life.
"Yeah, and it kind of surprised me a little bit," Derek confessed.
"Because I did believe that was kind of, like, a mutual thing. It wasn't like she pinned me down against the bed or anything like that and kind of initiated everything."
"Things led up to it -- from kisses and all that stuff that I'm not going to talk about," Derek added.
Jamie insisted Derek could talk about everything on Unfiltered, but he just laughed her comment off.
"We're all ears!" Jamie joked.
"But yeah, it's good to know now. So, it's definitely interesting," Derek noted.
Derek was then asked how it felt to hear Katie say he needed "more game" behind closed doors.
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"Umm, I don't. I wouldn't say I do agree with it," Derek shared. "I'm definitely still kind of more reserved with this stuff because I just met her. So I'm not going to whip out these crazy things."
Jamie laughed about how Derek could definitely "whip them out" now because Katie seemed "ready for it."
"Yeah, it appears so. It would appear so, so we'll see what happens!" Derek acknowledged.
Married at First Sight expert Dr. Viviana Coles joined Derek on Unfiltered and offered some advice on how to initiate intimacy in a relationship.
"Well, it's very unique in this situation because you can't assume that they're into each other right off the bat," Viviana said of the pairs of strangers who wed on MAFS.
"That has to be something that you prove to each other. Now some couples will never have sex during this experience, but they still show each other that they're into each other in other ways."
Viviana suggested affection can be shown in ways other than through sexual acts.
"I would say sex is just one way to show that they are into each other. Just because I don't have my penis inside you doesn't mean I don't want you! You need to look at other things!" Viviana shared with a laugh.
Katie worried she was going to fall hard for her husband only for him to reject her later on and realize he couldn't love her.
But Derek was growing sick and tired of Katie repeatedly talking about his dating history and asking for reassurance about their future together. Derek called it "bullsh-t" and didn't think it was crazy he hadn't met the right person yet at age 27.
"I don't f-cking know what's going to happen at the end of this," Derek said, before storming off with frustration in a recent episode. "I think it's f-cked up it's being held against me."
However, Derek later apologized to Katie for snapping at her, and Katie expressed how she was sorry for bringing up the same concern all the time.
Derek at least acknowledged he had "a crush" on Katie and said he felt optimistic about where their relationship was headed -- and Katie did too, as long as Derek promised not to lose his temper like that again.
"I forgive you, and I'm sorry for, I guess, dwelling on the issue. And I will stop," Katie said.
"I don't want to break your heart," Derek noted. "But don't break mine."