The objective of this pilot study is to evaluate the feasibility and efficacy of Rhexium Onco Nutrition, HDT-202 for post-operative care in patients who have undergone gastrectomy.

1. A total of 4 visits will be performed.
2. At the screening visit,subject's written informed consent, assessing the inclusion/exclusion criteria and assigning enrollment numbers to eligible subjects, demographic information taking, medical history/medication history taking, vital signs measuring, physical examination, height and body weight measuring, instructing how to install/use the investigational device, and administering quality of life questionnaires.
3. During the treatment period, a total of 3 visits will be performed. To evaluate feasibility and efficacy, the following procedures will be carried out: vital signs measuring, physical examination, nutrition assessment/consultation, evaluation of feasibility for 'subjects', evaluation of feasibility for 'investigators', and adverse events (AEs)/concomitant medications checking and collecting.
4. During the treatment period, telephone monitoring is conducted depending on the compliance of subjects.

Inclusion Criteria:

1. Patient who voluntarily signs the informed consent form for this study
2. Age of ≥19 years old
3. Patient who has undergone therapeutic gastrectomy after a diagnosis of gastric cancer
4. Able to eat food orally after gastrectomy
5. Patient who possesses an Android OS based mobile device and is capable of using the investigational device.

Exclusion Criteria:

1. Other cancer or metastasis documented within 5 years prior to screening
2. Ongoing or planned enteral tube feeding or total parenteral nutrition
3. Other clinically significant medical or psychiatric findings based on which the individual is considered by the investigator to be ineligible
4. Individual who possesses a mobile device on which the application is unable to be installed and/or run normally for technical reasons
5. Individual who, in the opinion of the investigator, has difficulty understanding how to use the investigational device or is unlikely to comply with other study procedures