Souma is really susceptible to cracking up, and even memories will put him into laughing fits. But being self-conscious about this, he always tries to hide it. When he does this again at a clothing store his friend works at, the friend asks him why he does that, especially when it's so easy to tell anyway. Later, Shun also repeats the same sentiment...
Why do you always try to 
hide it when you laugh?
لماذا تحاول دوماً أن تخفي ابتسامتك؟
Warum versuchst du ständig,
es zu verstecken?
¿Por qué siempre te escondes?
¿Por qué siempre te escondes?
Pourquoi tu te caches
à chaque fois ?
Perché ti nascondi sempre?
Por que sempre tenta
disfarçar quando ri?
Почему ты пытаешься скрывать смех?