As for why Letty and Reimu are living together, please refer to "KuromakuMiko" "KuromakuMiko"/「くろまくみこ」 is the label applied to the shipping of Letty and Reimu in the Japanese fandom. "Kuromaku"/「黒幕」/「くろまく」 lit. "Black curtain", meaning "mastermind" is a nickname for Letty, from the Sakuya scenario of Perfect Cherry Blossom. "Miko"/「みこ」 = shrine maiden = Reimu

Living at the Hakurei Shrine →

I see, I see... you were concerned about your weight, so you came to me for advice.

Is that so......

Although I have no idea why you chose me, since you're depending on me, I guess I gotta do it.

As expected of Letty; I'm counting on you!

No, surely you understand why.

Don't emphasize it.

... even so, is it really something to be so bothered about?

I mean, I wouldn't consider either of you to be fat.

Sugar-coating your words doesn't make any difference!

One day, it'll happen suddenly! (weight gain)

Ah, right...

just aerodynamically curvaceous. Reimu literally says "just one part of you is big" but that simply doesn't work in English.

Well, do whatever you like. Doesn't seem like it'll cause any nuisance to me anyway...

And so, do your best, Rumia!

Yep!

Now then, first, how about we choose a diet regime?

Wow, so many books!

I, uh, just happened to pick them up in the meadow. There's no way I'm collecting these, okay?

Is that so—? ......hm? What's this apple diet?

That's a good one. How about this tomato diet?

Ah, this protein diet is good!