The speech sound tsu (つ) is one of the sounds that many learners of the Japanese language are not able to pronounce very well. It is a common mistake made by learners to pronounce tsu (つ) as chu (ちゅ) or su (す) . The tsu (つ) is a sound pronounced with the tongue in a position for ‘t’ before immediately making the su (す) sound. If you are unable to pronounce tsu (つ) , try saying su (す) once you have brought the tip of your tongue in contact with the back of your lower teeth.
Those learners whose mother tongues do not have this sound, for example English, French, Spanish, Portuguese, Korean, Indonesian, Malay, Thai, Lao, Vietnamese, Cambodian, Burmese, Arabian, Turkish etc. need to pay special attention to this.