Using Hiragana, how would you write a word/transcribe a sound which ends in a consonant? Such as 'kon'. Relevant to this, I don't understand why 'hajimemashite' doesn't pronounce the 'shi' in the word, and why in the phrase 'watashi wa ______ desu' the 'su' isn't pronounced, and in 'watashi wa _______ to iimasu', again, the 'su' isn't pronounced. Is there a grammatical reason for this?
I am really afraid to say this, but I assume you are a quite beginner.
Therefore, I would like to help you somehow, but since your question is too abstract, I can not help you unfortunately. HOWEVER, both ta and su are consonants. Only when written in English, it "looks like" they are ending in vowels. In Japanese, they are consonants.