I found the way to call OSLC API without user id and password.
Two-legged OAuth Sample
The example of the result is the following.
GET https://local.jkebanking.net/ccm/resource/itemName/com.ibm.team.workitem.WorkItem/1
Authorization: OAuth oauth_token="", oauth_consumer_key="187d851a1ecc4daeb6bcce7122151d14", oauth_signature_method="HMAC-SHA1", oauth_timestamp="1583219842", oauth_nonce="1106358187910800", oauth_version="1.0", oauth_signature="lPTNgP8%2FSVb1lYwjEePEZIxpKrY%3D"
HTTP/1.1 200 OK
Date: Tue, 03 Mar 2020 07:17:24 GMT
X-Powered-By: Servlet/3.0
Strict-Transport-Security: max-age=31536000
ETag: "5fd414fe-462b-311c-b88c-6e4b147278c6"
Last-Modified: Tue, 08 Oct 2019 07:24:19 GMT
Expires: Tue, 03 Mar 2020 07:17:24 GMT
OSLC-Core-Version: 2.0
Vary: Accept,OSLC-Core-Version
Set-Cookie: JSESSIONID=0000ZqQpsii2HajnEM3SrbYgjRN:5f941c41-44d7-4f23-8125-2e6f1daf1222; Path=/; Secure; HttpOnly
Cache-Control: private, must-revalidate, max-age=0, no-cache=set-cookie
Keep-Alive: timeout=10, max=100
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: application/rdf+xml;charset=UTF-8
Content-Language: ja-JP
<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:dcterms="http://purl.org/dc/terms/"
xmlns:rtc_ext="http://jazz.net/xmlns/prod/jazz/rtc/ext/1.0/"
xmlns:oslc="http://open-services.net/ns/core#"
xmlns:acp="http://jazz.net/ns/acp#"
xmlns:oslc_cm="http://open-services.net/ns/cm#"
xmlns:oslc_cmx="http://open-services.net/ns/cm-x#"
xmlns:oslc_pl="http://open-services.net/ns/pl#"
xmlns:acc="http://open-services.net/ns/core/acc#"
xmlns:rtc_cm="http://jazz.net/xmlns/prod/jazz/rtc/cm/1.0/"
xmlns:process="http://jazz.net/ns/process#" >
<rdf:Description rdf:about="https://local.jkebanking.net/ccm/resource/itemName/com.ibm.team.workitem.WorkItem/1">
<oslc_cmx:project rdf:resource="https://local.jkebanking.net/ccm/oslc/projectareas/_IH1G4TMdEemPEpj6Q2FHPw"/>
<rtc_cm:progressTracking rdf:resource="https://local.jkebanking.net/ccm/oslc/workitems/_O78fNzMdEemPEpj6Q2FHPw/progressTracking"/>
<rdf:type rdf:resource="http://open-services.net/ns/cm#ChangeRequest"/>
<rtc_cm:timeSheet rdf:resource="https://local.jkebanking.net/ccm/oslc/workitems/_O78fNzMdEemPEpj6Q2FHPw/rtc_cm:timeSheet"/>
<oslc_cm:inprogress rdf:datatype="http://www.w3.org/2001/XMLSchema#boolean">false</oslc_cm:inprogress>
<oslc:shortId rdf:datatype="http://www.w3.org/2001/XMLSchema#string">1</oslc:shortId>
<dcterms:type rdf:datatype="http://www.w3.org/2001/XMLSchema#string">障害</dcterms:type>
<oslc_cm:reviewed rdf:datatype="http://www.w3.org/2001/XMLSchema#boolean">false</oslc_cm:reviewed>
<oslc:instanceShape rdf:resource="https://local.jkebanking.net/ccm/oslc/shapes/workitems/_O78fNzMdEemPEpj6Q2FHPw"/>
<dcterms:creator rdf:resource="https://local.jkebanking.net/jts/users/deb"/>
<oslc_cm:closed rdf:datatype="http://www.w3.org/2001/XMLSchema#boolean">false</oslc_cm:closed>
<oslc_pl:schedule rdf:resource="https://local.jkebanking.net/ccm/oslc/workitems/_O78fNzMdEemPEpj6Q2FHPw/schedule"/>
<oslc_cm:status rdf:datatype="http://www.w3.org/2001/XMLSchema#string">新規</oslc_cm:status>
<dcterms:subject rdf:datatype="http://www.w3.org/2001/XMLSchema#string">値, ウェアハウス, インストール</dcterms:subject>
<acc:accessContext rdf:resource="https://local.jkebanking.net/ccm/acclist#_IH1G4TMdEemPEpj6Q2FHPw"/>
<dcterms:identifier rdf:datatype="http://www.w3.org/2001/XMLSchema#string">1</dcterms:identifier>
<dcterms:modified rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2019-10-08T07:24:19.150Z</dcterms:modified>
<rtc_cm:due rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2019-10-10T01:00:00.000Z</rtc_cm:due>
<acp:accessControl rdf:resource="https://local.jkebanking.net/ccm/oslc/access-control/_IH1G4TMdEemPEpj6Q2FHPw"/>
<rtc_cm:resolvedBy rdf:resource="https://local.jkebanking.net/jts/users/unassigned"/>
<rtc_cm:type rdf:resource="https://local.jkebanking.net/ccm/oslc/types/_IH1G4TMdEemPEpj6Q2FHPw/defect"/>
<rtc_cm:repository rdf:resource="https://local.jkebanking.net/ccm/oslc/repository"/>
<oslc_cmx:priority rdf:resource="https://local.jkebanking.net/ccm/oslc/enumerations/_IH1G4TMdEemPEpj6Q2FHPw/priority/priority.literal.l11"/>
<rtc_ext:contextId rdf:datatype="http://www.w3.org/2001/XMLSchema#string">_IH1G4TMdEemPEpj6Q2FHPw</rtc_ext:contextId>
<oslc:serviceProvider rdf:resource="https://local.jkebanking.net/ccm/oslc/contexts/_IH1G4TMdEemPEpj6Q2FHPw/workitems/services"/>
<rtc_cm:modifiedBy rdf:resource="https://local.jkebanking.net/jts/users/clmadmin"/>
<rtc_cm:state rdf:resource="https://local.jkebanking.net/ccm/oslc/workflows/_IH1G4TMdEemPEpj6Q2FHPw/states/com.ibm.team.workitem.defectWorkflow/com.ibm.team.workitem.defectWorkflow.state.s1"/>
<oslc:shortTitle rdf:parseType="Literal">障害 1</oslc:shortTitle>
<rtc_cm:plannedFor rdf:resource="https://local.jkebanking.net/ccm/oslc/iterations/_IKziZzMdEemPEpj6Q2FHPw"/>
<rtc_cm:filedAgainst rdf:resource="https://local.jkebanking.net/ccm/resource/itemOid/com.ibm.team.workitem.Category/_O4ErsjMdEemPEpj6Q2FHPw"/>
<dcterms:title rdf:parseType="Literal">ユーザー・パスワードの変更不可</dcterms:title>
<process:iteration rdf:resource="https://local.jkebanking.net/ccm/process/iterations/_IKziZzMdEemPEpj6Q2FHPw"/>
<oslc_cmx:severity rdf:resource="https://local.jkebanking.net/ccm/oslc/enumerations/_IH1G4TMdEemPEpj6Q2FHPw/severity/severity.literal.l3"/>
<oslc_cm:fixed rdf:datatype="http://www.w3.org/2001/XMLSchema#boolean">false</oslc_cm:fixed>
<oslc_cm:verified rdf:datatype="http://www.w3.org/2001/XMLSchema#boolean">false</oslc_cm:verified>
<dcterms:contributor rdf:resource="https://local.jkebanking.net/jts/users/marco"/>
<rtc_cm:estimate rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">3600000</rtc_cm:estimate>
<oslc:discussedBy rdf:resource="https://local.jkebanking.net/ccm/oslc/workitems/_O78fNzMdEemPEpj6Q2FHPw/rtc_cm:comments"/>
<rtc_cm:subscribers rdf:resource="https://local.jkebanking.net/jts/users/deb"/>
<dcterms:created rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2019-01-21T00:12:46.080Z</dcterms:created>
<dcterms:description rdf:parseType="Literal">ユーザーがパスワードを変更できるようにするには、UI の追加が必要である。</dcterms:description>
<process:projectArea rdf:resource="https://local.jkebanking.net/ccm/process/project-areas/_IH1G4TMdEemPEpj6Q2FHPw"/>
<oslc_cm:approved rdf:datatype="http://www.w3.org/2001/XMLSchema#boolean">false</oslc_cm:approved>
<rtc_ext:archived rdf:datatype="http://www.w3.org/2001/XMLSchema#boolean">false</rtc_ext:archived>
</rdf:Description>
</rdf:RDF>