A Study of Tocilizumab in Chinese Participants With Systemic Juvenile Idiopathic Arthritis (sJIA)

Inclusion Criteria: * Participants meeting International League of Associations for Rheumatology (ILAR) classification for sJIA * Greater than (\>) 6 months of documented persistent sJIA activity prior to screening * Active disease * hsCRP \>4.3 milligrams per liter (mg/L) or 0.43 milligrams per deciliter (mg/dL) * Participant who has recovered from any symptomatic serositis for at least 30 days prior to the screening visit, and requires a dose of CSs at baseline of \</=30 mg/day or \</=0.5 mg/kg/day, whichever is less * Participants meeting one of the following: Participant who is not receiving MTX or discontinued MTX \>/=4 weeks prior to baseline visit; participant who has been taking MTX \>/=12 weeks immediately prior to the baseline visit and on a stable dose of \</=20 mg/m\^2 for \>/=8 weeks prior to the baseline visit, together with either folic acid or folinic acid according to local standard of care * Participant who was never treated with biologics or, if was previously treated with biologics, discontinued etanercept (or Yisaipu, Qiangke, or Anbainuo) \>/=2 weeks, infliximab or adalimumab \>/=8 weeks, anakinra \>/=1 week, or abatacept \>/=12 weeks prior to the baseline visit * Participant who is not currently receiving oral CSs, or is taking oral CSs at a stable dose for \>/=2 weeks prior to the baseline visit at \</=30 mg/day or \</=0.5 mg/kg/day, whichever is less * Participant who is not taking NSAIDs, or taking \</=1 type of NSAID at a stable dose for \>/=2 weeks prior to the baseline visit and is less than or equal to the maximum recommended daily dose Exclusion Criteria: * Wheelchair bound or bedridden participant * Any other autoimmune, rheumatic disease, or overlap syndrome other than sJIA * Participant who is not fully recovered from recent surgery or \<6 weeks since surgery at the time of screening visit; or planned surgery during the initial 12 weeks of the study * Lack of peripheral venous access * Any significant concurrent medical or surgical condition that would jeopardize the participant's safety or ability to complete the trial * Evidence of serious uncontrolled concomitant diseases * Asthma for which the participant has required the use of oral or parenteral CSs for \>/=2 weeks within 6 months prior to the baseline visit * Known human immunodeficiency (HIV) infection or other acquired forms of immune compromise or congenital conditions characterized by a compromised immune system * Any active acute, subacute, chronic, or recurrent bacterial, mycobacterial, viral, or systemic fungal infection or opportunistic infection * Any major episode of infection requiring hospitalization or treatment during screening, treatment with IV antibiotics completing within 4 weeks of the screening visit, or oral antibiotics completing within 2 weeks of the screening visit * History of atypical tuberculosis (TB) * Active TB requiring treatment within 2 years prior to screening visit * Positive purified protein derivative (PPD) or T-spot test (interferon-gamma \[IFN-γ\]-based test) at screen * Positive for latent TB * History of reactivation or new onset of a systemic infection such as herpes zoster or Epstein-Barr virus (EBV) within 2 months of the screening visit * Hepatitis B surface antigen (Ag)- or hepatitis C antibody (Ab)-positive * History of macrophage activation syndrome (MAS) within 3 months prior to the screening visit * Evidence of active malignant disease or diagnosed malignancies * Uncontrolled diabetes mellitus * Previous treatment with tocilizumab * Intra-articular, intramuscular, IV, or long-acting CSs administration within 28 days prior to the baseline visit * Treatment with non-biologic disease-modifying antirheumatic drugs (DMARDs; other than MTX) within 6 weeks prior to the baseline visit * Treatment with leflunomide that was not followed by standardized cholestyramine washout and documented to be below the limit of detection prior to the baseline visit * Treatment with cyclophosphamide, etoposide (VP16) and statins within 90 days prior to the baseline visit * Treatment with growth hormone and androgens within 4 weeks prior to the baseline visit * Administration of IV immunoglobulin within 28 days prior to the baseline visit * Treatment with any cell-depleting therapies * Stem cell transplant at any time * Participant who has received live or attenuated vaccines within 4 weeks prior to the baseline visit, or intending to receive while on study drug or 3 months following the last dose of study drug