being tough on someone but actually caring about them
Yuyushiki’s Yui is quite tough with especially Yuzuko but she clearly cares, even contemplating if she is too harsh on her while she sleeps. Azunyan is strict with Yui, but it might not be enough to make her tsundere. Aya is a clear romantic tsundere like Ayano and Hidamari Sketch’s Natsume.
Most tsunderes are tsundere because they are to shy to show their affection, but not all shy characters are tsundere.
For example Aikawa in Yuyushiki is shy but not a tsundere.
Technically you could be tsundere without being shy, for example if you are straightforward but haven’t learned how to express affection. I don’t know an example of this though.
Tsundere is either
Yuyushiki’s Yui is quite tough with especially Yuzuko but she clearly cares, even contemplating if she is too harsh on her while she sleeps. Azunyan is strict with Yui, but it might not be enough to make her tsundere. Aya is a clear romantic tsundere like Ayano and Hidamari Sketch’s Natsume.
Most tsunderes are tsundere because they are to shy to show their affection, but not all shy characters are tsundere. For example Aikawa in Yuyushiki is shy but not a tsundere. Technically you could be tsundere without being shy, for example if you are straightforward but haven’t learned how to express affection. I don’t know an example of this though.