The purpose of this study is to evaluate the efficiency and safety of a digital therapeutics(ET-101) for mild cognitive impairment (MCI).

This is a randomized, sham-controlled, assessor-blinded, 24-week parallel study.

100 MCI patients will be randomly assigned to two groups. The control group will be provided with a sham device.

Inclusion Criteria:

1. 55-85 years old

2. Patients diagnosed with mild cognitive impairment according to Petersen criteria

   1. A person with subjective memory complaints
   2. Memory degradation of z-score ≤ -1 from the normal range of age, gender, and level of education in the memory area of the CREAD-NP or SNSB battery
   3. The functional performance of overall cognitive function and daily life ability is sufficiently preserved.
   4. Not dementia

3. MMSE 27 or less

4. Adequate vision and hearing for clinical trial

5. Global CDR 0.5

6. If approved AD treatment drugs(AChEI, memantine, or both) are being administered, they should be administered at a stable dose for at least 12 weeks prior to randomization.

7. Have an identified trial partner (defined as someone who can assist the subject during the trial and spends at least 8 hours per week with the subject). The test partner must provide informed consent. This partner must also be willing and able to provide follow-up information to the subject during the trial. In the opinion of the investigator, the trial partner should spend sufficient time with the subject on a regular basis to ensure that the trial requirements are met. The permanent study partner does not have to live in the same residence as the subject. For study partners not residing with the subject, the investigator should ensure that the subject can easily contact the study partner while the study partner is not with the subject. If it is uncertain whether a subject's care arrangement is suitable for selection, the investigator should discuss this with the Medical Monitor. The trial partner should participate directly in visits where the clinical evaluation of CDR, EQ-5D, ADCS MCI-ADL are performed.

8. No difficulty in using mobile applications using smartphone

   1. A person who owns his/her smartphone
   2. A person who can call his/her guardian using smartphone by himself/herself

9. No difficulty in reading and writing Korean

10. Willingness and ability to comply with all aspects of the clinical trial protocol

Exclusion Criteria:

1. History of a transient ischemic attack(TIA), stroke, seizure within 12 months

2. Psychiatric symptoms that include;

   1. History of diagnosis of psychiatric disorders or symptoms that may interfere with the subject's testing procedure (e.g., psychosis, major depression)
   2. Responding "yes" to item 4 or 5 to suicidal ideation part of C-SSRS or any suicidal behavior within 6 months prior to screening, at screening or at randomization visit, or being hospitalized or treated for suicidal behavior in the past 5 years prior to screening

3. All other clinically significant abnormalities, such as

   1. Physical examinations, neurological examinations, and vital signs at screening or baseline that, in the opinion of the investigator, may require additional examination or treatment that may interfere with the study procedure or safety
   2. Other medical conditions (e.g., heart, respiratory, gastrointestinal, kidney disease) that are not adequately stable controlled or that, in the investigator's opinion, may affect the safety of the subject or interfere with the evaluation of the trial

4. A known or suspected history of drug or alcohol abuse or dependence within 2 years prior to screening

5. Prohibited concomitant medication

6. Surgery that requires general anesthesia is scheduled during the trial period.If only local anesthesia is required and the surgery is the day case without hospitalization after surgery or if, in the opinion of the investigator, the operation does not interfere with the test procedure and the safety of the subject, they should not be excluded

7. History of any type(online/offline) of cognitive intervention or participation in clinical trial regarding cognitive intervention within 12 months