As Issei looked over the fifteen women Riser had just summoned, he quickly realized two things. One, Riser's Peerage was literally made around the typical harem you'd find in a harem manga, the little sister, the Loli, the twins, the Priestess, the tomboy, the Kuudere, the main girl all of it. That leads us into the second thing Issei noticed.
"Um, Lord Riser, I think you forgot a piece."
Riser grew furious. "And who are you to say something like that to Riser?!"
Issei grew a bit terrified, but stood strong. "S-sorry, I just noticed that you didn't have a specific stereotype in that little harem of yours!"
Riser's anger dimmed as he looked at Issei with a bit of confusion in his eyes. "Oh, and what would that be, if you're so wise on the subject?"
Issei gulped, but gave a response. "W-well, you're missing a trap."
At this, Riser grew confused for a second, so Issei clarified. "You know, an extremely feminine, submissive male that usually makes the watchers of those types of series question their sexuality, and is usually a fan favorite, and the one way too many people want the main character to be with?"
Riser thought for a second before his eyes widened and he started panicking. "Oh my Lucifer, you're right! Riser would be willing to give this little Peerage here an extra month of training on top of the two weeks if you," at this, he points at Issei. "Help Riser get that last member of his harem! Seriously, how did I forget that?!"
Issei perked up at that. "Deal! Pres, can you excuse me from my contracts while I do this? He clearly needs to find this member for his harem to be truly complete, and as a fellow pervert and harem enthusiast, I can't let his harem to go unfinished!"
(Yeah, this idea popped in my head when I was looking through Riser's Peerage and noticed no trap amongst them/while I was working on my Issei x trap harem. This is in no way related to it, so do t worry, but go read it if you want. Anyways, this was kinda just fun to write, so I hope you enjoy! Have a nice day.)