They are adverbs and strengthen the meaning of the sentences.
1, "zehi" expresses a request and a hope. So we usually use"zehi"



" zehi" "kitto" "kanarazu"
| ZEHI | KITTO | KANARAZU | |
| a hope | Kare ni zehi kite moraitai.  Kare ni zehi kite hoshii.  | 
//////////////// | Kare ni kanarazu kite moraitai. Kare ni kanarazu kite hoshii.  | 
| a request  (a order)  | 
(contains  feeling of wish) Zehi kite kudasai. /////////////////////  | 
(contains  feeling of expectation) Kitto kite kudasai ne. ////////////////////////  | 
(contains  feeling of conviction) Kanarazu kite kudasai. Kanarazu kinasai.  | 
| a  determination  | 
////////////////// | Kitto ikimasu. | Kanarazu ikimasu. | 
| an inference | ////////////////// | ( subjective inference)  Kare wa kitto kuru desyo. Kare wa kitto kuru hazuda. Kare wa kitto kuru ni chigainai.  | 
( objective inference Kare wa kanarazu kuru desyo. Kare wa kanarazu kuru hazuda. Kare ha kanarazu kuru ni chigainai.  | 
| a conviction | /////////////////// | (subjective conviction)  Kare wa kitto kuru. Kono kusuri o nomeba kitto naoru. Kare wa kitto dokushin yo.  | 
(objective conviction)  Kare wa kanarazu kuru. Kono kusuri o nomeba kanarazu naoru. ///////////////////////  | 
| a certain result  (natures law habit...)  | 
//////////////////// | //////////////////// | Haru ni nareba kanarazu 
hana ga saku.  Kare wa asa kanarazu ha o migaku.(a habit)  | 
 /// JAPAN CULTURE STUDY GROUP ///