Hmm, about Miyuki... *goes to dig up
summer vacation chapter Vol5 Ch1* (Dang, never actually checked the dang volume cover till now
)
Found it:
Spoiler:
Shizuku asked Miyuki what does she feel about him. Miyuki replied she loves him. Shizuku asks if that is as a man or as a brother. Miyuki replied it's not as a man, because:
"I respect Onii-sama more than anyone, I love Onii-sama more than anyone. But this love isn't as a woman. My feelings towards Onii-sama is definitely not romantic love. Between me and Onii-sama it's impossible to have romantic love."
Miyuki knew why Shizuku asked - she's worried that Miyuki might get in the way of Honoka's attempts to win Tatsuya's heart. Sure, Miyuki will get jealous of Honoka being close to Tatsuya but it it can't be helped she'll acknowledge it.
3 years ago Miyuki died, and Tatsuya brought her back to life. Miyuki thinks because her life was given to her by her brother, everything she has belongs to Tatsuya:
"The feelings I have for Onii-sama isn't romantic love (恋爱) [...] Romantic love means you sought for the other person, right? [...] Become mine, seeking for the other person, that's love isn't it? [...] But there isn't a single thing I want from my Onii-sama. Because, I already have got myself from Onii-sama. [...] I won't seek anything else from my Onii-sama. Not even wanting him to accept my feelings. The only expression to describe this emotion... there's only 'love', and nothing else."
Miyuki admits she's distorted/twisted in thinking this way as well.
tl;dr - Miyuki's not a love interest for Tatsuya, at least at this point.