Investigation of Arrhythmogenic Effect of NPC-15 (NPC-15-7)

Inclusion Criteria: * Subject with BMI ≥ 17.6 kg/m2 and \< 30.0 kg/m2. * Subject who falls asleep at between 21:00 and 25:00 and wakes up at between 5:00 and 9:00 during 1 week prior to the first study drug administration. * Subject who is able to comply with the study requirements during the study period. Exclusion Criteria: * Subject with QTcF interval greater than 450 ms in male or greater than 470 ms in female on the 12-lead electrocardiogram (ECG), or with clinically significant ECG abnormalities in other findings. * Subject who has a family history of Torsades de Pointes (TdP) or long QT syndrome. * Subject who has a history of hypersensitivity or allergies to melatonin or ramelteon. * Subject who has a current or a history of disease which is considered inappropriate to be involved in the study, or who has any current disease to require treatments. * Subject who received any non-prescription or prescription drug within 2 weeks prior to the first study drug administration. * Subject who received any product containing St Jones Wart or any supplement containing melatonin within 4 weeks prior to the first study drug administration. * Subject who has a history of smoking habit or was possibly exposed to passive smoking on a daily basis within 24 weeks prior to the first study drug administration. * Subject who, in the opinion of the investigator or sub-investigator, is unsuitable to be involved in the study.