I don't think I wear shipping googles, true that it is only really confirmed for the 3 cited but there are some moments which clearly hint romantic attraction, especially because I would not like Tatsuya to have too much females falling for him, harem can be cool but it is better when it's played for laughs like in vol, 13 in this series at least.
First I will use Miyuki has an example.
Spoiler for My reasons:
Did we need vol 11 to know that she wanted Tatsuya's D? That scene with her attacking him with psion surge was more than enough. Everything she said to Shizuku in vol 5 was not important for me.
Mayumi: I ship her with Tatsuya but despite their moments in the 9SC I didn't believe she loved him, even with Mari's remark and that she said to see him as a brother. Then we got Vol 5 and Yokohama. Why was she comparing her body to Miyuki in her bathroom, thinking that she was unnoticed by Tatsuya? Why was she jealous of Suzune, asking if she was his type? And so on.
And lastly Erika, most of the readers don't think so but when I gather the pieces together I am convinced that she indeed loves him. You have her monologue about him before her date + Mizuki's thoughts comparing her feelings for Tatsuya to her 2 other male friends Leo and Mikihiko + her jealousy in Visitor arc followed by a discussion with Mizuki. It's more than enough for me at least. And it's still in character considering her behaviour and past.
I don't understand people putting Shizuku in all of this however, even with vol 12she shown nothing but pure admiration and does her best to help Honoka since day 1. The problem with the anime is that with such a large number of female characters and their blushing, Tatsuya looks like a harem king
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