Short spoiler : Still no truth yet, they actually went inside a love hotel, the black box returns
Long spoiler : We begin with Naoto sitting on a bed, and Luna looking fresh after taking a bath. Naoto thinks Luna would just hole up the whole time, but Luna took the opportunity to take a bath since they would be spending the night. Luna, still in bath robes, lies on the bed while Naoto averts his eyes. Naoto lets Luna take the bed while he heads off to the sofa but Luna stops him. With the bed big enough, she doesn't mind sharing, and reminds him that they used to do the same back in the past. Naoto gives in and convinces himself that it would only be for one night, and nothing really changed compared to sleeping back at her place, the only exception being that Luna would be sleeping beside him.
While Naoto is busy convincing himself, Luna turns the TV on and... starts watching porn(curse you, black box!)... as one does in a love hotel. Naoto grabs the remote and asks her what she is doing, but Luna replies by saying that goes along the line of "when in a love hotel, might as well enjoy themselves with the amenities". Luna fires back by saying Naoto was getting excited himself after checking out the fridge and the bathtub that lights up, Naoto then turns the TV off.
Luna then spots a small brochure for birthday discounts, and it reminds her that Naoto's birthday is coming up. Naoto corrects her by saying his birthday was on the 22nd of April(start of school year), and it's already too late to celebrate. This surprises Luna and argues that they always celebrate his birthday on the 22nd of August, when they're on the countryside. Naoto explains that because they only meet during summer break, he told her his birthday was on August, because otherwise they won't be able to celebrate it together.
Luna asks why he didn't tell her sooner, but Naoto tells her that he couldn't at the time, which was when he moved in with her, thinking she'd notice when he went drinking that one time... she didn't. Naoto tells her that there's always next year, but Luna relents on celebrating it within the year.
Luna asks if there's something that Naoto wants, or wants her to do for him. Naoto averting his gaze from a nipple slip(curse you, black box!), tells her he doesn't have anything that he wants at the moment, and we get a flashback scene.
In a situation similar to the current one, past!Luna asks past!Naoto what he wants for his birthday. She doesn't have much money, so she asks if there's something she can do for him instead. This being after Naoto saw her seemingly kissing a guy, Naoto asks for a kiss, which caught Luna by surprise because he wants it immediately. She moves in, but Naoto closes his eyes, unaware that Luna was aiming for his forehead. Luna then tells him that once he gets older, she'll give him a proper kiss, and we're back in the present.
After the two seemingly recalled their past promise, the chapter ends with Luna presenting herself for the kiss as Naoto moves closer and closer.