why do i often see the character "tsu" as furigana but it is not actually pronounced ?

You had misidentify the "tsu" as a full-sized character, when it should be smaller, which is a Sokuon.

The sokuon is used for various purposes. The main use is for showing a geminate consonant, which is represented in rōmaji by the "doubling" of the following consonant.

Example:

けってい = 決定

け ke

っ sokuon

て te, with the sokuon representing the doubling of the t consonant.

い i

You can read more about it here:

http://www.sljfaq.org/w/sokuon

I agree with Cabbage Patch.

Who cares what 田中 wrote? It's usually wrong most of the time. She's from Argentina so it's not like she's fluent in English.

Besides, quite a few of us on Answers strongly suspect that Cabbage Patch and 田中 are the same person who's just using multiple accounts.

対戦相手決定= たいせないてけってい

The tsu is small, so it acts as a double constant. Taisenaite kettei.

早くやろうぜ　一回戦= はやくやろういっかいせん

Hayaku yarou ikkaisen

All it does is double the constant after it. って= tte.

Get it?

TSU (つ) is not a double "constant"! The function of tsu(つ) in this case, just doubles the first "consonant" of the next syllable / word.

"ketsutei" is wrong: it's けつてい or ke+つ+te+i so, the t of tei gets doubled: kettei

"itsukaisen" is wrong: it's いつかいせん or i+つ+ka+i+se+n, so the k of kaisen gets doubled: ikkaisen

Note:

constant = something that never changes, that is it stays the same.

consonant = something in an alphabet which is not defined as a vowel.

Yeah, っ is a double consonant.

Who cares if 田中 wrote it as 'constant' she's not even American for God's sake, she's from Argentina if you look at her profile.

Anyways, it's Taisen aite kettei, hayaku yarouze ikkaisen.

It's a little tsu,not a big one. I'll put them next to eachother for you.

っつ

See the difference?