Haha, role reversal.
Momo and Nana look more alike when they were younger.
At school, Lala fixes Nana's transporter phone while Momo and Rito watch. Momo accuses Nana of playing with the phone too much and once again makes fun of Nana's flat chest. On the mention of the topic, Lala pulls out a new invention that gives Nana instant breast enlargement, but unexpectedly it also turns Momo into a flat chest. The effects don't last long though, and Momo and Nana go back to squabbling and complaining to Lala.
Later at the nurse's room, Rito and Momo chat with Mikado-sensei and Oshizu. When asked by Oshizu, Momo explains that Lala has been coming up with weird inventions as far as she could remember. Momo recalls one time seven years ago when she and Nana were arguing, Lala's robo-pets suddenly all went wild. Nana and Momo had to help Lala collect the pets, and later Lala was lectured by Zastin. At this moment, Mea shows up at the door looking for Nana. After learning Nana is at the store, Mea comments that Mikado looks beautiful and leaves. Momo asks Mikado if she knows anything about Mea and her master, and Mikado states she doesn't have any concrete details for now but will keeping looking into it.
To Love-Ru Darkness is in danger of ending prematurely.
On the weekend, Rito, Nana, Momo and Yami visit Mea's apartment. Momo is hoping to see if there is any valuable intel but Mea's apartment is mostly empty. Days later, Rito, Yami, Momo, Mikado and Oshizu have a chat about Mea outside of the school during break time. Momo states that even though Mea appears to be melding into the group, Momo is feeling even more uneasy. Momo feels there is still a wall separating Mea, and there is something dark beyond that wall. Yami states that perhaps she and Mea are different because they were created as weapons, but RIto disagrees and cites Yami's friendship with Mikan as an example of how Yami can feel affection just like other people. Suddenly, Oshizu is approached by a stray dog and this causes her psychokinetic powers to go crazy. In the chaos, Oshizu strips Yami of her panties and Yami ends up sitting on Rito's face. Momo grabs Rito and bolts from the school as Yami gives chase, and thus the meeting is adjourned.
After school, Rito is approached by Ren who was tasked by Run to hand Rito her newest CD. Ren then asks what are Rito's feelings for Lala and Run and tells Rito not to do anything that will make a girl cry. After the conversation, Rito wonders how he should proceed but then his mind wanders into Momo's harem scenario. Rito's face turns red, and this is seen by Yami who is nearby.
Later at home, Mikan tells Rito to tell the princesses that it's dinner time. Rito climbs into the Devilukean sister's apartment and into Lala's room, and he sees that Lala is still working on her inventions. Rito wonders why Lala started inventing stuff, and Lala answers that she started out of boredom because there wasn't much else to do when she was living in the palace. Outside the room, Momo hears Rito's voice and fantasizes about Rito and Lala making out, but then realizes that Lala is on some levels even more childish than Nana. Nana also appears and she and Momo decide to listen in on the conversation. Back in the room, Rito recalls what Momo told her about Lala's inventions running wild, but Peke interrupts and states that Lala did it on purpose so that Momo and Nana would stop arguing. Rito realizes Lala really loves her sisters and at the same time starts blushing as well. Lala goes to check on Rito but she accidentally activates one of her inventions which proceeds to tie her and Rito together in a compromising position.
Lala and her perverted malfunctioning inventions.
On the roof top, Momo and Nana realizes that Lala is an awesome big sister and they are the ones who are immature after overhearing Lala and Rito's conversation. Back on the first floor, Mikan wonders why nobody is coming down for dinner.
This episode mostly covered only one chapter of material, with some small bits from another chapter. I don't recall if that managa chapter was particularly long, but this episode didn't feel too slow.
The episode focused on the relationship between the three Devilukean princesses and marks the first time that Lala actually got some spotlight in Darkness. Lala may not be the main female character anymore, but she still lives in Rito's house and is an integral part of Momo's harem plan. This episode shows that Lala may seem immature and simple-minded sometimes, she does have the big sister mentality and takes care of Momo and Nana in her own way. To sum it up, this was a cute little side story.
Apparently there will be no new episode next week, so it'll be two weeks until the next new episode.