Change From Baseline at Week 24 in the Visual Analogue Scale (VAS) Score for Pain;Change From Baseline at Week 24 in the Functional Assessment of Chronic Illness Therapy (FACIT) Fatigue Score;Relapse-Free Rate During the DB Period;Annualized Relapse Rate (ARR) During the DB Period;Change From Baseline in Modified Rankin Scale (mRS) Scores at 24 Week Intervals During the DB Period;Change From Baseline in Zarit Burden Interview (ZBI) Scores at 24 Week Intervals During the DB Period;Change From Baseline in Expanded Disability Status Scale (EDSS) Scores at 24 Week Intervals During the DB Period;Change From Baseline in Visual Acuity (Snellen Chart) at 24 Week Intervals During the DB Period;Change From Baseline in Short Form Generic Health Survey (SF-36) Mental Component Summary Scores at 24 Week Intervals During the DB Period;Change From Baseline in SF-36 Physical Component Summary Scores at 24 Week Intervals During the DB Period;Change From Baseline in SF-36 Bodily Pain Domain Scores at 24 Week Intervals During the DB Period;Change From Baseline in SF-36 General Health Domain Scores at 24 Week Intervals During the DB Period;Change From Baseline in SF-36 Mental Health Domain Scores at 24 Week Intervals During the DB Period;Change From Baseline in SF-36 Physical Functioning Domain Scores at 24 Week Intervals During the DB Period;Change From Baseline in SF-36 Role-Emotional Domain Scores at 24 Week Intervals During the DB Period;Change From Baseline in SF-36 Role-Physical Domain Scores at 24 Week Intervals During the DB Period;Change From Baseline in SF-36 Social Role Functioning Domain Scores at 24 Week Intervals During the DB Period;Change From Baseline in SF-36 Vitality Domain Scores at 24 Week Intervals During the DB Period;Change From Baseline in EuroQoL-5 Dimensions (EQ-5D) Index Scores at 24 Week Intervals During the DB Period;Serum Satralizumab Concentration During the DB Period;Serum Soluble IL-6 Receptor (sIL-6R) Concentration During the DB Period;Serum High Sensitivity C-Reactive Protein (hsCRP) Concentration During the DB Period;Serum Interleukin-6 (IL-6) Concentration During the DB Period;Number of Participants With at Least One Adverse Event in the DB Period;Number of Participants With at Least One Serious Adverse Event in the DB Period;Number of Participants With Non-Serious Adverse Events of Special Interest in the DB Period;Number of Participants With Selected Adverse Events in the DB Period;Number of Participants With Suicidal Behaviors and Ideations Collected by Columbia-Suicide Severity Rating Scale in the DB Period;Blood Anti-Aquaporin-4 (AQP4) Antibody Concentration Over Time;Percentage of Blood Plasmablast Over Time;Percentage of Participants With Anti-Drug Antibodies to Satralizumab in the DB Period