A sairentodere is a dere type that is quiet but not necessarily shy like a dandere, they just don't like to speak much. Some can can be physically mute, while others will only speak when they feel it necessary to do so. They can be heavily observant as well. Contrary to kuudere they don't act expressionless. A sairentodere can also be really energic and happy without saying a word, while a kuudere can talk a lot while still not showing emotions whatsoever.