Katsumi wants to try it herself.

K-T was looking down at his crotch but was panicking. It seemed like the device had not worked. His dick was gone but there wasn't anything else in its place.

"Emily! It went wrong. Nothing switched with my dick!" he said in alarm.

"Silly brother, of course it worked. Look better. What am I, some third rate hack?" she replied swatting him on the back of the head.

At the same time he lowered his hand to check what was down there, his eyes rose up to check the screen. The he saw Katsumi, proudly sporting his massive erect cock on her crotch. He discovered that he had received her cleanly shaven pussy in exchange for his dick.

"Please wash your hands everytime before touching this, in fact it would be even better if you refrained from touching it at all." She instructed him, his sister swatting his hand away from his crotch. "Oh and under no circumstances can you have intercourse with anything else than my husband's penis, I take my wedding vows very seriously."

"But you took my thing to have some fun with it, it's not fair. You'll probably are going to use it to do some weird stuff with a dude. How long are we going to be switched anyway?" he asked.

"I think a good week of testing is warranted. But I notice that you were eager to try out having a vagina. Whose penis did you want in it anyway?" she replied.

"Well, no, not really. It's just a matter of principle, double standards and that. I just would like to get my things back soon. Now that you duplicated my sister's device you can use it on anything, you don't really need me." he explained, blushing at his curiosity about what sex would feel with this kind of equipment (as curious as to what it would feel the other way around, still being a virgin).

"I had considered switching you with my husband now, so we could get some second honeymoon while switching places. But sadly it isn't possible it would still be your penis in my vagina and that would be unfaithful. So we will have to do with his existing holes." She explained.

"Wait! I could do it!" proposed Lily. K-T really didn't get what she meant.

"Please explain what you mean?" asked Katsumi.

"Easy, you switch me with your husband. That way it would be my vagina that you would be testing on him, not yours and if I help K-T with his new fantasy it will be your husband's penis going in your vagina, keeping you faithful." She replied.

"An interesting use a simple transposition logic for someone without scientific training. Perfectly satisfactory. I need to warn you though that my husband's penis is really pathetic and almost unusable. It will require a lot of efforts to get anything out of it."

"It's no problem. K-T knows how those work, he'll help me."

While they exchanged and totally excluded K-T from the conversation, Katsumi had applied a device on her husband and his sister was fiddling in the front of Lily's pants to do the same.

It was an horrible irony that for a week it would be his very own massive dick that would ravage his crush's pussy, while he was not only such with the wrong equipment but Lily wanted to help him test it with something barely the size of his thumb.

The only view of Lily's vagina that he got was on a depressed japanese man through a screen. She was now equipped with a shriveled penis and thought that she had somehow done him a favor while doing so.