Inclusion Criteria:

          1. Have gastric and gastroesophageal junction adenocarcinoma

          2. Untreated and cT2-4 and/or cN+ without evidence of metastatic disease

          3. Patients at least 20 years of age on the day of providing consent.

          4. Patients with a performance status of 0 or 1 on the Eastern Cooperative Oncology
             Group.

          5. Patients with adequate organ function at the time of enrollment as defined below:

               -  Neutrophil count ≥1500mm3

               -  Platelet count ≥10 × 100,000/mm3

               -  Hemoglobin (Hb) ≥ 9.0 g/dL,

               -  Total bilirubin ≤1.5 mg/dL

               -  AST (GOT) and ALT (GPT) ≤ 100 IU/L

               -  Creatinine ≤1.5 mg/dL

               -  Urinary protein : It satisfies one of the following (if any of the inspection
                  criteria are satisfied, other examination may not be carried out) (i) urinary
                  protein (test paper method) is 2+ or less (ii) Urine Protein Creatinine (UPC)
                  ratio <3.5 (iii) 24-hour urine protein was measured, urinary protein ≦ 3500 mg

               -  International normalized ratio (INR) ≤ 1.5

          6. Patients who not received a blood transfusion within 14 days of registration.

          7. Patients have recovered adverse events associated with radiation and surgical
             operation as pretreatment to Grade 1 or less or baseline or less with CTCAE v5.0
             excluding stable symptoms. However, adverse events with stable symptoms even with
             Grade 2 or higher excluded.

          8. Female of childbearing potential who are negative in a pregnancy test within 14 days
             before enrollment. Both male and female patients should agree to use an adequate
             method of contraception (total abstinence or use of a male condom plus partner use of
             contraceptive method [an intrauterine device or hormone releasing system, a
             contraceptive implant and an oral contraceptive]) starting with the first dose of
             study therapy through 120 days after the last dose of study therapy. Duration will be
             determined when the subject is assigned to treatment.

          9. Patients capable of taking oral medication.

         10. Patients who provided written informed consent to be subjects in this study.

        Exclusion Criteria:

          1. Patients who have undergone surgical treatment and radiotherapy within 2 weeks before
             enrollment.

          2. Patients with hypertension that is difficult to control (systolic blood pressure ≥160
             mmHg and diastolic blood pressure ≥90 mmHg) despite treatment with several hypotensive
             agents.

          3. Patients with acute coronary syndrome (including myocardial infarction and unstable
             angina), and with a history of coronary angioplasty or stent placement performed
             within 6 months before enrollment.

          4. Patients with a history of New York Heart Association congestive heart failure of
             grade II or above, unstable angina, myocardial infarction.

          5. Patients have an addigional active malignancy (except for definitively treated
             melanoma in-situ, basal or squamous cell carcinoma of the skin, or carcinoma in-situ
             of the cervix) within the past 24 months.

          6. Patients have severe (hospitalization required) complications (intenstinal palsy,
             intestinal obstruction, pulmonary fibrosis, diabetes difficult to control, heart
             failure, myocardial infarction, unstable angina, renal failure, liver failure, mental
             disease, cerebrovascular disease etc).

          7. Patients with a history of a gastrointestinal perforation and /or gastrointestinal
             fistula within 6 months before enrollment.

          8. Is infected with active hepatitis B (defined as HBs antigen positive) or hepatitis C.

          9. Patients with a history of human immunodeficiency virus (HIV).

         10. Patients with a history of (non-infectious) pneumonitis that required steroids or has
             current pneumonitis.

         11. Patients who are administered live vaccines <30 days before the initiation of
             treatment with the investigational drug.

         12. Patients with concurrent autoimmune disease, or a history of chronic or recurrent
             autoimmune disease.

         13. Patients who require systemic corticosteroids (excluding temporary usage for tests,
             prophylactic administration for allergic reactions, or to alleviate swelling
             associated with radiotherapy) or immunosuppressants, or who have received such a
             therapy <14 days before enrollment.

         14. Patients have serious non-healing wound, ulcer, or bone fracture.

         15. Females who are pregnant or breastfeeding.

         16. Patients have no intention to comply with the protocol or cannot comply.

         17. Patients were judged unsuitable as subject of this study by investigator.