trap-Kei > all

Smitten by the girl in gothic lolita that he saw at the shop, Sawaki visits everyday. However, he has not caught sight of her since, and asks the old shopowner, Kikuji (the microbe monster), about her. Kikuji replies that they aren't employing any girl by that description. During class, Sawaki is asked by Oikawa to go shopping with her.
However, Sawaki decides to drop by the shop again, neglecting his promise to Oikawa. He is in luck today, he spots the girl. She calls him by his full name, and he blushes to find out that she knows of him. That does not last long, however, as he leans in for a closer look of her face and realizes that 'she' is actually Kei. (About time.)

*squint*
Oikawa passes by, wondering why Sawaki would bail on her, when she sees him with Kei. The two boys don't seem to notice that she's there, and, with Oikawa watching, Kei kisses Sawaki on the lips. (Much to the latter's horror.)

…

BRACE FOR IMPACT.

BAM.

What the f-
It is then that Sawaki notices Oikawa, adding salt to the wound. Oikawa is about to leave, but Kei pushes Sawaki to go with her.
The shopping trip involves buying one thing - a cooling mat for Oikawa's apartment. Due to the weight, Oikawa needs Sawaki to help her carry it to her apartment. Oikawa's apartment is a testament to her fastidiousness - Sawaki is unable to see a microbe anywhere.

FEBREZE.
After setting up the mat, Oikawa serves them curry. She asks Sawaki is there is anything 'special' about him, citing a few curious situations that centered around him. Sawaki does not respond, so she changes the subject to Kei. She asks him if that 'girl' is his girlfriend, and that she will root for him. Sawaki decides not to let Oikawa know that the 'she' is actually Kei.
The next day, Misato and Takuma consult Sawaki regarding two pieces of suspicious-looking bread. Sawaki replies that he sees no microbes, so the two chow down. Haruka wants Sawaki's help with her Ph.D dissertation, but he reminds her that he sees microbes much differently than how they look.

Obligatory microbes shot.
After Sawaki leaves, Professor Itsuki comes by to inform Misato and Takuma that the bread they are eating is spoiled.
In the restroom, Misato and Takuma begin to question whether or not Sawaki has lost his ability. Through much constipation consideration, they conclude that he has, and as his friends they should keep it a secret from Professor Itsuki and Haruka. As further indication of this, Sawaki finds it odd that 'everyone's quiet today'.
Passing by the shop again, Oikawa sees Kei and stops to chat. The main topic of their conversation is Sawaki, even after Oikawa tries to steer from it. Oikawa asks Kei if 'she' likes Sawaki, and Kei says that he does. (In a very roundabout way. Also, wut?) Kei says that Oikawa seems like Sawaki's type, and reminisces about the first time he saw her. Of course, there's no way that trap-Kei was there at the time, and amidst Oikawa's confusion he realizes that Sawaki hadn't said anything to Oikawa.

I dunno, does he?

How indeed?
Meanwhile, Misato and Takuma want to help Sawaki get a part-time job, for the purpose of keeping him away from Professor Itsuki's lab. They do not get far, bumping into Haruka almost immediately, who tells Sawaki to come with her. In the lab, Haruka confronts Sawaki with her suspicion: that he can no longer see microbes.

Ohmygosh what is he going to do n- oh, there's only one episode left.

Thoughts:
It was pretty funny to see that Sawaki being attracted to trap-Kei… until he found out that it was Kei. We find out that Oikawa is interested in older men, but it's pretty clear that she has a very easygoing relationship with Sawaki. However, whether that will go anywhere seems doubtful, unless they hit us with a timeskip next episode.
As for Kei admitting that he likes Sawaki …I'm unsure about this. He could have said it as a friend, but the other route is also open. I'm leaning toward the former, since Kei had thought Oikawa knew his identity.
With Sawaki apparently losing his microbe-seeing ability, it is made rather clear this is the second-to-last episode.