The purpose of this study is to assess the safety and tolerability of TAK-994 and to determine the effect of TAK-994 (compared to placebo) on sleepiness, as measured by mean sleep latency on the maintenance of wakefulness Test (MWT), in an acute sleep phase delay paradigm in healthy participants.

The drug being tested in this study is called TAK-994. The study will evaluate the safety/tolerability, PD, and PK of TAK-994 in an acute sleep phase delay paradigm in healthy participants.

The study will enroll up to approximately 18 healthy participants. Participants will be randomly assigned to 1 of the 3 treatment sequences which will remain undisclosed to the participant and study doctor during the study (unless there is an urgent medical need):

• TAK-994 Dose A + Placebo + TAK-994 Dose B
• TAK-994 Dose B + TAK-994 Dose A + Placebo
• Placebo + TAK-994 Dose B + TAK-994 Dose A

This single center trial will be conducted in the United States. The overall time to participate in this study is approximately 10 weeks. Participants will be followed up remotely on Day 7 after the last dose of study drug for a follow-up assessment.

Inclusion Criteria:

1. Be a current nonsmoker who has not used tobacco- or nicotine-containing products (example, nicotine patch) for at least 6 months prior to the first dose of study drug.
2. Have regular sleep-wake habits (example, routinely spending 6.5 to 8 hour sleeping nightly, not oversleeping by more than 3 hour on weekends [that is, total sleep not more than 11 hour]) as determined by investigator interviews and confirmed in 5-day actigraphy records and regularly fall asleep between 9:30 PM and 12:00 AM.

Exclusion Criteria:

1. Have a positive alcohol or drug screen or a history of alcohol consumption exceeding 2 standard drinks per day on average (1 glass is approximately equivalent to: beer [354 mL/12 ounces], wine [118 mL/4 ounces], or distilled spirits [29.5 mL/1 ounce] per day).
2. Have excessive sleepiness, defined by a self-reported Epworth Sleepiness Scale (ESS) score at screening greater than (>) 10; irregular work hours; or routine night-shift work within 1 month before randomization.
3. Have a prior history of or currently is experiencing any known/suspected sleep disorder (including obstructive sleep apnea and restless leg syndrome), any disorder associated with excessive daytime sleepiness (EDS), or any diagnosis interfering with assessment of sleepiness.
4. At the time of screening, be receiving treatment with nasal/oronasal positive airway pressure for any reason.
5. Have abnormal findings on the initial polysomnography conducted on Day -1 (check-in) of the first treatment period.
6. Have traveled across 2 or more time zones within the 2 weeks before screening.
7. Have caffeine consumption of more than 400 milligram (mg)/day for 2 weeks before screening (1 serving of coffee is approximately equivalent to 120 mg of caffeine).

Takeda makes patient-level, de-identified data sets and associated documents available after applicable marketing approvals and commercial availability have been received, an opportunity for the primary publication of the research has been allowed, and other criteria have been met as set forth in Takeda's Data Sharing Policy (see www.TakedaClinicalTrials.com/Approach for details). To obtain access, researchers must submit a legitimate academic research proposal for adjudication by an independent review panel, who will review the scientific merit of the research and the requestor's qualifications and conflict of interest that can result in potential bias. Once approved, qualified researchers who sign a data sharing agreement are provided access to these data in a secure research environment.