Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
Akinori Kosaka
Table title:
Club statistics
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=3 rowspan=1 > Club performance </th><th colspan=2 rowspan=1 > League </th><th colspan=2 rowspan=1 > Cup </th><th colspan=2 rowspan=1 > League Cup </th><th colspan=2 rowspan=1 > Total </th></tr>
<tr> <th colspan=1 rowspan=1 > Season </th><th colspan=1 rowspan=1 > Club </th><th colspan=1 rowspan=1 > League </th><th colspan=1 rowspan=1 > Apps </th><th colspan=1 rowspan=1 > Goals </th><th colspan=1 rowspan=1 > Apps </th><th colspan=1 rowspan=1 > Goals </th><th colspan=1 rowspan=1 > Apps </th><th colspan=1 rowspan=1 > Goals </th><th colspan=1 rowspan=1 > Apps </th><th colspan=1 rowspan=1 > Goals </th></tr>
<tr> <th class="highlighted"  colspan=3 rowspan=1 > Japan </th><th colspan=2 rowspan=1 > League </th><th colspan=2 rowspan=1 > Emperor's Cup </th><th colspan=2 rowspan=1 > J.League Cup </th><th colspan=2 rowspan=1 > Total </th></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > 1998 </td><td class="highlighted"  colspan=1 rowspan=5 > Omiya Ardija </td><td class="highlighted"  colspan=1 rowspan=1 > Football League </td><td colspan=1 rowspan=1 > 23 </td><td colspan=1 rowspan=1 > 9 </td><td colspan=1 rowspan=1 > 3 </td><td colspan=1 rowspan=1 > 0 </td><td colspan=2 rowspan=1 >  </td><td colspan=1 rowspan=1 > 32 </td><td colspan=1 rowspan=1 > 9 </td></tr>
<tr> <td colspan=1 rowspan=1 > 1999 </td><td colspan=1 rowspan=4 > J2 League </td><td colspan=1 rowspan=1 > 22 </td><td colspan=1 rowspan=1 > 2 </td><td colspan=1 rowspan=1 > 3 </td><td colspan=1 rowspan=1 > 3 </td><td colspan=1 rowspan=1 > 1 </td><td colspan=1 rowspan=1 > 1 </td><td colspan=1 rowspan=1 > 26 </td><td colspan=1 rowspan=1 > 6 </td></tr>
<tr> <td colspan=1 rowspan=1 > 2000 </td><td colspan=1 rowspan=1 > 21 </td><td colspan=1 rowspan=1 > 2 </td><td colspan=1 rowspan=1 > 1 </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 2 </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 24 </td><td colspan=1 rowspan=1 > 2 </td></tr>
<tr> <td colspan=1 rowspan=1 > 2001 </td><td colspan=1 rowspan=1 > 23 </td><td colspan=1 rowspan=1 > 4 </td><td colspan=1 rowspan=1 > 1 </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 1 </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 25 </td><td colspan=1 rowspan=1 > 4 </td></tr>
<tr> <td colspan=1 rowspan=1 > 2002 </td><td colspan=1 rowspan=1 > 10 </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 0 </td><td colspan=2 rowspan=1 >  </td><td colspan=1 rowspan=1 > 10 </td><td colspan=1 rowspan=1 > 0 </td></tr>
<tr> <th colspan=1 rowspan=1 > Country </th><th colspan=2 rowspan=1 > Japan </th><th colspan=1 rowspan=1 > 99 </th><th colspan=1 rowspan=1 > 17 </th><th colspan=1 rowspan=1 > 8 </th><th colspan=1 rowspan=1 > 3 </th><th colspan=1 rowspan=1 > 4 </th><th colspan=1 rowspan=1 > 1 </th><th colspan=1 rowspan=1 > 111 </th><th colspan=1 rowspan=1 > 21 </th></tr>
<tr> <th colspan=3 rowspan=1 > Total </th><th colspan=1 rowspan=1 > 99 </th><th colspan=1 rowspan=1 > 17 </th><th colspan=1 rowspan=1 > 8 </th><th colspan=1 rowspan=1 > 3 </th><th colspan=1 rowspan=1 > 4 </th><th colspan=1 rowspan=1 > 1 </th><th colspan=1 rowspan=1 > 111 </th><th colspan=1 rowspan=1 > 21 </th></tr>
</table>
Question:
When did Akinori Kosaka join the Japan Football League club?
Answer:
Akinori Kosaka joined Japan Football League club Omiya Ardija in 1998.