Who Does Tatsuya End up with?

In Volume 16, after Maya announced Miyuki as her heir, she also announced the engagement of Tatsuya and Miyuki; this made Tatsuya Miyuki's fiancé.

Is Mayumi in love with Tatsuya?

Mayumi weakly and unconvincingly objects to the facts. It is hinted that she likes Tatsuya and her feelings became more prevalent after she regularly loses her confidence in her speech, frequently display outbursts and capricious mannerisms whenever he is mentioned or present.

Are Tatsuya and Miyuki the same age?

Miyuki is the daughter of Shiba Tatsurou and the late Shiba Miya and is eleven months younger than her only elder brother, Tatsuya (her birthday falls on March 25, a month before Tatsuya's birthday). They are mostly mistaken as twins for being in the same year.