I'm a Royal Tutor in My Sister's Dress is a manga series written by Sakurana Haru and Mizuki Nomura.
Ordinary boy Sherlock Doyle finds that his genius sister Glinda has abandoned her post as a royal tutor and that unless he takes her place they could both be executed. He finds himself having to teach maths to the kings five young children, while attempting to stop anybody finding about his true gender.
!!''I'm A Royal Tutor In My Sister's Dress'' provides examples of:
* ChildProdigy: Seira.
* DraggedIntoDrag: Sherlock.
* DudeLooksLikeALady: It helped Sherlock to pretend to be his sister.
** Seira acts like one of these.
** And the youngest son, Shin, seems like an EmotionlessBoy.
* SugarAndIcePersonality: Seira.
* TeenGenius: Glinda.
* TricksterTwins: Sarasa and Orie.
* WhatIf: One side story about what'd happen if Sherlock wasn't an example of DudeLooksLikeALady. He expected it'd make Helmut give up the plan to pass him up as Glinda but to no avail. He was deemed a masculine girl and the only girls he attracted were masculine as well. [[spoiler:He was glad it was AllJustADream]].
* WholesomeCrossdresser: Sherlock.