A:とうして まつやま さん が すき てす か。Why do you like Matsuyama?
B. さあ….まつやまさん な かわいし、けっこ だ し、 はんさむ な おとこ の ひと だ し。 uhmm..Because Matsuyama is cute,wonderful and a handsome man.
We use ‘shi’ or し when we want to state many reasons consecutively. It is placed after an adjective or the reason itself. For the example above ,
i-adjective ‘ Kawaii ‘ became ‘kawaishi’. Replace last i with shi. Because he is cute.
na-adjective ‘kekko na’ became kekko da shi. Replace na with ‘da shi’. Because he s wonderful.
Also a reason ending in desu, will result to desu becoming dashi. Like for the example above , ” hansamu na otoko no hito desu” became ”hansamu na otoko no hito da shi” . Because he’s a handsome man.
Summary.
i adjective — drop i, add shi
Na adjective — drop na, add da shi
Reason desu — drop desu, add da shi
How about you? Why do you like a certain person?